diff --git a/src/circuit/CircuitDefinition.js b/src/circuit/CircuitDefinition.js
index fdfa7839..085a0064 100644
--- a/src/circuit/CircuitDefinition.js
+++ b/src/circuit/CircuitDefinition.js
@@ -153,7 +153,7 @@ class CircuitDefinition {
         if (newStateIndex !== undefined) {
             newVal = newStateIndex;
         }
-        if (newVal === undefined) {
+        if (newVal === undefined || newVal === 0) {
             m.delete(wire);
         } else {
             m.set(wire, newVal);
diff --git a/test/circuit/CircuitDefinition.test.js b/test/circuit/CircuitDefinition.test.js
index bab7788b..0024c07e 100644
--- a/test/circuit/CircuitDefinition.test.js
+++ b/test/circuit/CircuitDefinition.test.js
@@ -1310,6 +1310,21 @@ suite.test("gateAtLocIsDisabledReason_multiwireOperations", () => {
 
 });
 
+suite.test("withSwitchedInitialStateOn", () => {
+    let c = circuit(`-
+                     -`);
+    assertThat(c.customInitialValues).isEqualTo(new Map());
+
+    c = c.withSwitchedInitialStateOn(0);
+    assertThat(c.customInitialValues).isEqualTo(new Map([[0, '1']]));
+
+    c = c.withSwitchedInitialStateOn(0);
+    assertThat(c.customInitialValues).isEqualTo(new Map([[0, '+']]));
+
+    c = c.withSwitchedInitialStateOn(0, 0);
+    assertThat(c.customInitialValues).isEqualTo(new Map());
+});
+
 suite.test("colCustomContextFromGates", () => {
     let c = circuit(`-A-B-
                      -A-A-