diff --git a/js-assembler/runtime-src/baselib-modules.js b/js-assembler/runtime-src/baselib-modules.js
index d8b9f2e..fa80519 100644
--- a/js-assembler/runtime-src/baselib-modules.js
+++ b/js-assembler/runtime-src/baselib-modules.js
@@ -74,7 +74,7 @@
     // Returns the offset into the prefix in which the value will be stored.
     ModuleRecord.prototype.getPrefixOffset = function(externalName) {
         var i;
-        for (i = 0; i < this.prefix.names; i++) {
+        for (i = 0; i < this.prefix.names.length; i++) {
             if (this.prefix.names[i] === externalName) {
                 return i;
             }
diff --git a/version.rkt b/version.rkt
index 218bb28..45c1905 100644
--- a/version.rkt
+++ b/version.rkt
@@ -7,4 +7,4 @@
 (provide version)
 (: version String)
 
-(define version "1.187")
+(define version "1.188")