diff --git a/cranelift/codegen/src/cursor.rs b/cranelift/codegen/src/cursor.rs
index 56ce840626..c95aa5a3fb 100644
--- a/cranelift/codegen/src/cursor.rs
+++ b/cranelift/codegen/src/cursor.rs
@@ -794,15 +794,20 @@ impl<'c, 'f> ir::InstInserterBase<'c> for &'c mut EncCursor<'f> {
         if !self.srcloc.is_default() {
             self.func.srclocs[inst] = self.srcloc;
         }
-        // Assign an encoding.
-        // XXX Is there a way to describe this error to the user?
-        #[cfg_attr(feature = "cargo-clippy", allow(clippy::match_wild_err_arm))]
-        match self
-            .isa
-            .encode(&self.func, &self.func.dfg[inst], ctrl_typevar)
-        {
-            Ok(e) => self.func.encodings[inst] = e,
-            Err(_) => panic!("can't encode {}", self.display_inst(inst)),
+
+        // Skip the encoding update if we're using a new (MachInst) backend; encodings come later,
+        // during lowering.
+        if self.isa.get_mach_backend().is_none() {
+            // Assign an encoding.
+            // XXX Is there a way to describe this error to the user?
+            #[cfg_attr(feature = "cargo-clippy", allow(clippy::match_wild_err_arm))]
+            match self
+                .isa
+                .encode(&self.func, &self.func.dfg[inst], ctrl_typevar)
+            {
+                Ok(e) => self.func.encodings[inst] = e,
+                Err(_) => panic!("can't encode {}", self.display_inst(inst)),
+            }
         }
 
         &mut self.func.dfg
diff --git a/tests/all/fuzzing/issue1809.wat b/tests/all/fuzzing/issue1809.wat
new file mode 100644
index 0000000000..e7508e2613
--- /dev/null
+++ b/tests/all/fuzzing/issue1809.wat
@@ -0,0 +1,485 @@
+(module
+  (type $t0 (func (result i32)))
+  (type $t1 (func (param i32)))
+  (type $t2 (func (param i32) (result i32)))
+  (func $hello (export "hello") (type $t0) (result i32)
+    (local $l0 i32)
+    (if $I0
+      (i32.eqz
+        (local.tee $l0
+          (call $f2)))
+      (then
+        (unreachable)))
+    (i32.store8 offset=4
+      (local.get $l0)
+      (i32.const 42))
+    (local.get $l0))
+  (func $goodbye (export "goodbye") (type $t1) (param $p0 i32)
+    (call $f4
+      (local.get $p0)))
+  (func $f2 (type $t0) (result i32)
+    (local $l0 i32) (local $l1 i32) (local $l2 i32)
+    (global.set $g0
+      (local.tee $l1
+        (i32.sub
+          (global.get $g0)
+          (i32.const 16))))
+    (i32.store offset=12
+      (local.get $l1)
+      (i32.load
+        (i32.const 1048576)))
+    (block $B0
+      (br_if $B0
+        (local.tee $l0
+          (call $f3
+            (i32.add
+              (local.get $l1)
+              (i32.const 12)))))
+      (local.set $l0
+        (i32.const 0))
+      (br_if $B0
+        (i32.eq
+          (local.tee $l2
+            (memory.grow
+              (i32.const 1)))
+          (i32.const -1)))
+      (i32.store
+        (local.tee $l0
+          (i32.shl
+            (local.get $l2)
+            (i32.const 16)))
+        (i32.add
+          (local.get $l0)
+          (i32.const 65643)))
+      (i32.store offset=4
+        (local.get $l0)
+        (i32.const 0))
+      (i32.store offset=8
+        (local.get $l0)
+        (i32.load offset=12
+          (local.get $l1)))
+      (i32.store offset=12
+        (local.get $l1)
+        (local.get $l0))
+      (local.set $l0
+        (call $f3
+          (i32.add
+            (local.get $l1)
+            (i32.const 12)))))
+    (i32.store offset=64
+      (i32.const 1048576)
+      (i32.load offset=12
+        (local.get $l1)))
+    (global.set $g0
+      (i32.add
+        (local.get $l1)
+        (i32.const 16)))
+    (local.get $l0))
+  (func $f3 (type $t2) (param $p0 i32) (result i32)
+    (local $l1 i32) (local $l2 i32) (local $l3 i32) (local $l4 i32) (local $l5 i32) (local $l6 i32)
+    (if $I0
+      (local.tee $l1
+        (i32.load
+          (local.get $p0)))
+      (then
+        (loop $L1
+          (local.set $l3
+            (i32.add
+              (local.get $l1)
+              (i32.const 8)))
+          (if $I2
+            (i32.and
+              (local.tee $l4
+                (i32.load offset=8
+                  (local.get $l1)))
+              (i32.const 1))
+            (then
+              (loop $L3
+                (local.get $l3)
+                (i64.load32_u
+                  (i32.and
+                    (local.get $l4)
+                    (i32.const -2)))
+                (local.set $l2
+                  (block $B4 (result i32)
+                    (drop
+                      (br_if $B4
+                        (i32.const 0)
+                        (i32.eqz
+                          (local.tee $l3
+                            (i32.and
+                              (local.tee $l4
+                                (i32.load offset=4
+                                  (local.get $l1)))
+                              (i32.const -4))))))
+                    (select
+                      (i32.const 0)
+                      (local.get $l3)
+                      (i32.and
+                        (i32.load8_u
+                          (local.get $l3))
+                        (i32.const 1)))))
+                (local.get $l1)
+                (if $I5
+                  (i32.eqz
+                    (i32.or
+                      (i32.eqz
+                        (local.tee $l5
+                          (i32.and
+                            (local.tee $l6
+                              (i32.load
+                                (local.get $l5)))
+                            (i32.const -4))))
+                      (i32.and
+                        (local.get $l6)
+                        (i32.const 2))))
+                  (then
+                    (i32.store offset=4
+                      (local.get $l5)
+                      (i32.or
+                        (i32.and
+                          (i32.load offset=4
+                            (local.get $l5))
+                          (i32.const 3))
+                        (local.get $l3)))
+                    (local.set $l3
+                      (i32.and
+                        (local.tee $l4
+                          (i32.load offset=4
+                            (local.get $l1)))
+                        (i32.const -4)))))
+                (i32.and
+                  (if $I6 (result i32)
+                    (local.get $l3)
+                    (then
+                      (i32.store
+                        (local.get $l3)
+                        (i32.or
+                          (i32.and
+                            (i32.load
+                              (local.get $l3))
+                            (i32.const 3))
+                          (i32.and
+                            (i32.load
+                              (local.get $l1))
+                            (i32.const -4))))
+                      (i32.load offset=4
+                        (local.get $l1)))
+                    (else
+                      (local.get $l4)))
+                  (i32.const 3))
+                (i32.store offset=4)
+                (local.get $l1)
+                (local.get $l1)
+                (i32.store
+                  (local.get $l2)
+                  (i32.and
+                    (local.tee $l1
+                      (unreachable))
+                    (i32.const 3)))
+                (if $I7
+                  (i32.and
+                    (local.get $l1)
+                    (i32.const 2))
+                  (then
+                    (i32.store
+                      (local.get $l2)
+                      (i32.or
+                        (i32.load
+                          (local.get $l2))
+                        (i32.const 6)))))
+                (i32.store
+                  (local.get $p0)
+                  (local.get $l2))
+                (local.set $l3
+                  (i32.add
+                    (local.get $l2)
+                    (i32.const 8)))
+                (br_if $L3
+                  (i32.and
+                    (local.tee $l4
+                      (i32.load offset=8
+                        (local.tee $l1
+                          (local.get $l2))))
+                    (i32.const -32))))))
+          (if $I8
+            (i32.ge_u
+              (i32.sub
+                (local.tee $l2
+                  (i32.and
+                    (i32.load
+                      (local.get $l1))
+                    (i32.const -4)))
+                (local.get $l3))
+              (i32.const 4))
+            (then
+              (loop $L9
+                (if $I10
+                  (i32.le_u
+                    (i32.add
+                      (local.get $l3)
+                      (i32.const 72))
+                    (i32.add
+                      (local.get $l2)
+                      (i32.const -4)))
+                  (then
+                    (local.tee $l2
+                      (i32.add
+                        (local.get $l2)
+                        (i32.const -12)))
+                    (i64.load32_u offset=8
+                      (i32.const 0))
+                    (i64.store align=4
+                      (local.get $l2)
+                      (i64.const 0))
+                    (local.get $l2)
+                    (i32.store
+                      (i32.load
+                        (local.get $l1))
+                      (i32.clz
+                        (i32.const -4)))
+                    (local.tee $l4
+                      (i32.load
+                        (local.get $l1)))
+                    (if $I11
+                      (i32.eqz
+                        (i32.or
+                          (i32.eqz
+                            (local.tee $p0
+                              (i32.const -1828)))
+                          (i32.and
+                            (local.get $l4)
+                            (i32.const 2))))
+                      (then
+                        (i32.store offset=4
+                          (local.get $p0)
+                          (i32.or
+                            (i32.and
+                              (i32.load offset=36
+                                (local.get $p0))
+                              (i32.const 3))
+                            (local.get $l2)))))
+                    (i32.store offset=4
+                      (local.get $l2)
+                      (i32.or
+                        (i32.and
+                          (i32.load offset=68
+                            (local.get $l2))
+                          (i32.const 19))
+                        (local.get $p0)))
+                    (i32.store
+                      (local.get $l1)
+                      (i32.or
+                        (i32.and
+                          (i32.load
+                            (local.get $l1))
+                          (i32.const 3))
+                        (local.get $l2)))
+                    (i32.store
+                      (local.get $l3)
+                      (i32.and
+                        (i32.load
+                          (local.get $l3))
+                        (i32.const -2)))
+                    (br_if $L9
+                      (i32.eqz
+                        (i32.xor
+                          (local.tee $p0
+                            (i32.load offset=2
+                              (local.get $l1)))
+                          (i32.const 2))))
+                    (i32.store offset=69
+                      (local.get $l1)
+                      (i32.and
+                        (local.get $p0)
+                        (i32.const -3)))
+                    (br_if $L1)
+                    (unreachable)
+                    (nop)
+                    (i32.or
+                      (i32.load offset=2)
+                      (i32.const 2))
+                    (i32.store)
+                    (br $L9)))
+                (i32.store offset=50
+                  (local.get $p0)
+                  (i32.and
+                    (local.get $l4)
+                    (i32.const -4)))
+                (local.set $l2
+                  (local.get $l1)))
+              (i32.store
+                (local.get $l2)
+                (i32.or
+                  (i32.load
+                    (local.get $l2))
+                  (i32.const 1)))
+              (return
+                (i32.add
+                  (local.get $l2)
+                  (i32.const 8)))))
+          (local.get $p0)
+          (br_table $L1 $L1 $L1 $L1
+            (i32.load offset=87
+              (local.get $l1)))
+          (unreachable)
+          (unreachable)
+          (unreachable))))
+    (i32.const 0))
+  (func $f4 (type $t1) (param $p0 i32)
+    (local $l1 i32) (local $l2 i32) (local $l3 i32) (local $l4 i32) (local $l5 i32) (local $l6 i32) (local $l7 i32)
+    (if $I0
+      (local.get $p0)
+      (then
+        (local.set $l6
+          (i32.load
+            (i32.const 1048576)))
+        (i32.store offset=2 align=1
+          (local.get $p0)
+          (i32.const 0))
+        (i32.store
+          (local.tee $l1
+            (i32.add
+              (local.get $p0)
+              (i32.const -8)))
+          (i32.and
+            (local.tee $l4
+              (i32.load
+                (local.get $l3)))
+            (i32.const -2)))
+        (block $B1
+          (block $B2
+            (loop $L3
+              (block $B4
+                (block $B5
+                  (loop $L6
+                    (block $B7
+                      (if $I8
+                        (local.tee $l3
+                          (i32.and
+                            (i32.load
+                              (local.tee $l5
+                                (i32.add
+                                  (local.get $p0)
+                                  (i32.const -4))))
+                            (i32.const -4)))
+                        (then
+                          (br_if $B7
+                            (i32.eqz
+                              (i32.and
+                                (local.tee $l7
+                                  (i32.load
+                                    (local.get $l3)))
+                                (i32.const 1))))))
+                      (br_if $L6
+                        (i32.div_s
+                          (i32.eqz
+                            (local.tee $l2
+                              (i32.and
+                                (local.get $l4)
+                                (i32.const -4))))
+                          (i32.and
+                            (local.get $l4)
+                            (i32.const 2))))
+                      (br_if $L6
+                        (i32.and
+                          (i32.load8_u
+                            (local.get $l2))
+                          (i32.const 1)))
+                      (i32.store
+                        (local.get $p0)
+                        (i32.and
+                          (i32.load offset=8
+                            (local.get $l2))
+                          (i32.const -4)))
+                      (i32.store offset=8
+                        (local.get $l2)
+                        (i32.or
+                          (local.get $l1)
+                          (i32.const 1)))
+                      (br $B2))
+                    (br_if $B5
+                      (i32.or
+                        (i32.eqz
+                          (local.tee $p0
+                            (i32.and
+                              (local.get $l4)
+                              (i32.const -20))))
+                        (i32.and
+                          (local.get $l4)
+                          (i32.const 3))))
+                    (i32.store offset=4
+                      (local.get $p0)
+                      (i32.or
+                        (i32.and
+                          (i32.load offset=4
+                            (local.get $p0))
+                          (i32.const 3))
+                        (local.get $l3)))
+                    (br_if $L3
+                      (i32.eqz
+                        (local.tee $l2
+                          (i32.and
+                            (local.tee $p0
+                              (i32.load
+                                (local.get $l5)))
+                            (i32.const -4)))))
+                    (local.set $p0
+                      (i32.and
+                        (i32.load
+                          (local.get $l1))
+                        (i32.const -4)))
+                    (local.get $l2)
+                    (local.get $l2)
+                    (local.set $l7
+                      (unreachable))
+                    (br $B4))
+                  (local.get $p0)
+                  (i64.load32_u
+                    (local.get $l6))
+                  (br $B1))
+                (local.set $l2
+                  (local.get $l3)))
+              (local.get $l2)
+              (local.get $l7)
+              (br_if $I0
+                (i32.eqz
+                  (local.tee $l2
+                    (i32.and
+                      (local.tee $p0
+                        (i32.const 125))
+                      (i32.const 16)))))
+              (local.set $p0
+                (unreachable)))
+            (i32.store
+              (local.get $l4)
+              (i32.and
+                (local.get $l3)
+                (i32.const 0)))
+            (i32.store
+              (local.get $l1)
+              (i32.and
+                (local.tee $p0
+                  (i32.load
+                    (local.get $l1)))
+                (i32.const 3)))
+            (br_if $B2
+              (i32.eqz
+                (i32.and
+                  (local.get $p0)
+                  (i32.const 2))))
+            (i32.store
+              (local.get $l3)
+              (i32.or
+                (i32.load
+                  (local.get $l3))
+                (i32.const 2))))
+          (local.set $l1
+            (local.get $l6)))
+        (i32.store
+          (i32.const 1048576)
+          (global.get $__data_efd)))))
+  (memory $memroy (export "memroy") 17)
+  (global $g0 (mut i32) (i32.const 1048576))
+  (global $__data_efd (export "__data_efd") i32 (i32.const 1048580))
+  (global $__heap_bare (export "__heap_bare") i32 (i32.const 1048580)))