diff --git a/src/cmd/compile/internal/ssa/prove.go b/src/cmd/compile/internal/ssa/prove.go
index a11b46566dd..371009a57d4 100644
--- a/src/cmd/compile/internal/ssa/prove.go
+++ b/src/cmd/compile/internal/ssa/prove.go
@@ -704,6 +704,9 @@ func addBranchRestrictions(ft *factsTable, b *Block, br branch) {
 		// When we branched from parent we learned a new set of
 		// restrictions. Update the factsTable accordingly.
 		d := tr.d
+		if d == signed && ft.isNonNegative(c.Args[0]) && ft.isNonNegative(c.Args[1]) {
+			d |= unsigned
+		}
 		switch br {
 		case negative:
 			switch b.Control.Op { // Special cases
diff --git a/test/prove.go b/test/prove.go
index b7ef468be63..f7b3ef0847b 100644
--- a/test/prove.go
+++ b/test/prove.go
@@ -605,6 +605,15 @@ func trans2(a, b []int, i int) {
 	_ = b[i] // ERROR "Proved IsInBounds$"
 }
 
+func trans3(a, b []int, i int) {
+	if len(a) > len(b) {
+		return
+	}
+
+	_ = a[i]
+	_ = b[i] // ERROR "Proved IsInBounds$"
+}
+
 //go:noinline
 func useInt(a int) {
 }