diff --git a/src/cmd/compile/internal/ssa/prove.go b/src/cmd/compile/internal/ssa/prove.go
index 4788f2d803..12c2580c95 100644
--- a/src/cmd/compile/internal/ssa/prove.go
+++ b/src/cmd/compile/internal/ssa/prove.go
@@ -1305,9 +1305,9 @@ func isNonNegative(v *Value) bool {
 	if !v.Type.IsInteger() {
 		panic("isNonNegative bad type")
 	}
-	if !v.Type.IsSigned() {
-		return true
-	}
+	// TODO: return true if !v.Type.IsSigned()
+	// SSA isn't type-safe enough to do that now (issue 37753).
+	// The checks below depend only on the pattern of bits.
 
 	switch v.Op {
 	case OpConst64:
diff --git a/test/fixedbugs/issue37753.go b/test/fixedbugs/issue37753.go
new file mode 100644
index 0000000000..ac311e3715
--- /dev/null
+++ b/test/fixedbugs/issue37753.go
@@ -0,0 +1,18 @@
+// run
+
+// Copyright 2020 The Go Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+package main
+
+//go:noinline
+func f(a, b uint) int {
+	return int(a-b) / 8
+}
+
+func main() {
+	if x := f(1, 2); x != 0 {
+		panic(x)
+	}
+}