diff --git a/.bumpy/fix-port-integer.md b/.bumpy/fix-port-integer.md
new file mode 100644
index 000000000..3f05b3529
--- /dev/null
+++ b/.bumpy/fix-port-integer.md
@@ -0,0 +1,5 @@
+---
+varlock: patch
+---
+
+Reject non-integer values for @type=port
diff --git a/packages/varlock/src/env-graph/lib/data-types.ts b/packages/varlock/src/env-graph/lib/data-types.ts
index ecf7fb680..8b21a53bb 100644
--- a/packages/varlock/src/env-graph/lib/data-types.ts
+++ b/packages/varlock/src/env-graph/lib/data-types.ts
@@ -545,9 +545,18 @@ const PortDataType = createEnvGraphDataType(
         if (rawVal.includes('.')) throw new CoercionError('Port number must be an integer');
         if (rawVal.includes('e')) throw new CoercionError('Port number should be an integer, not in exponential notation');
       }
-      return coerceToNumber(rawVal);
+      const numVal = coerceToNumber(rawVal);
+      // Unquoted schema values like 80.5 are already numbers after parse auto-coerce;
+      // the string '.' check above does not cover that path.
+      if (!Number.isInteger(numVal)) {
+        throw new CoercionError('Port number must be an integer');
+      }
+      return numVal;
     },
     validate(val) {
+      if (!Number.isInteger(val)) {
+        return new ValidationError('Port number must be an integer');
+      }
       if (settings?.min !== undefined && val < settings?.min) {
         return new ValidationError(`Min value is ${settings?.min}`);
       }
diff --git a/packages/varlock/src/env-graph/test/data-types.test.ts b/packages/varlock/src/env-graph/test/data-types.test.ts
index 2aac08f93..f7644f03d 100644
--- a/packages/varlock/src/env-graph/test/data-types.test.ts
+++ b/packages/varlock/src/env-graph/test/data-types.test.ts
@@ -44,6 +44,33 @@ describe('number data type - Infinity coercion', () => {
   });
 });
 
+describe('port data type', () => {
+  it('accepts integer ports', async () => {
+    const g = await loadAndResolve(outdent`
+      # @type=port
+      P=8080
+    `);
+    expect(g.configSchema.P.isValid).toBe(true);
+    expect(g.configSchema.P.resolvedValue).toBe(8080);
+  });
+
+  it('rejects non-integer numeric ports from schema auto-coerce', async () => {
+    const g = await loadAndResolve(outdent`
+      # @type=port
+      P=80.5
+    `);
+    expect(g.configSchema.P.isValid).toBe(false);
+  });
+
+  it('rejects non-integer string ports', async () => {
+    const g = await loadAndResolve(outdent`
+      # @type=port
+      P="80.5"
+    `);
+    expect(g.configSchema.P.isValid).toBe(false);
+  });
+});
+
 describe('url data type', () => {
   describe('prependHttps', () => {
     it('prepends https:// when missing', async () => {