diff --git a/src/ng/interpolate.js b/src/ng/interpolate.js
index 6b61e56f..05b1cf2f 100644
--- a/src/ng/interpolate.js
+++ b/src/ng/interpolate.js
@@ -178,10 +178,24 @@ function $InterpolateProvider() {
                 } else {
                   part = $sce.valueOf(part);
                 }
-                if (part === null || isUndefined(part)) {
+                if (part == null) { // null || undefined
                   part = '';
-                } else if (typeof part != 'string') {
-                  part = toJson(part);
+                } else {
+                  switch (typeof part) {
+                    case 'string':
+                    {
+                      break;
+                    }
+                    case 'number':
+                    {
+                      part = '' + part;
+                      break;
+                    }
+                    default:
+                    {
+                      part = toJson(part);
+                    }
+                  }
                 }
               }
               concat[i] = part;