diff --git a/app/assets/js/processbuilder.js b/app/assets/js/processbuilder.js
index 0f1ef8d..173501a 100644
--- a/app/assets/js/processbuilder.js
+++ b/app/assets/js/processbuilder.js
@@ -569,6 +569,24 @@ class ProcessBuilder {
         return mcArgs
     }
 
+    /**
+     * Ensure that the classpath entries all point to jar files.
+     * 
+     * @param {Array.<String>} list Array of classpath entries.
+     */
+    _processClassPathList(list) {
+
+        const ext = '.jar'
+        const extLen = ext.length
+        for(let i=0; i<list.length; i++) {
+            const extIndex = list[i].indexOf(ext)
+            if(extIndex > -1 && extIndex  !== list[i].length - extLen) {
+                list[i] = list[i].substring(0, extIndex + extLen)
+            }
+        }
+
+    }
+
     /**
      * Resolve the full classpath argument list for this process. This method will resolve all Mojang-declared
      * libraries as well as the libraries declared by the server. Since mods are permitted to declare libraries,
@@ -601,6 +619,8 @@ class ProcessBuilder {
         const finalLibs = {...mojangLibs, ...servLibs}
         cpArgs = cpArgs.concat(Object.values(finalLibs))
 
+        this._processClassPathList(cpArgs)
+
         return cpArgs
     }
 
@@ -733,6 +753,7 @@ class ProcessBuilder {
         }
         return libs
     }
+
 }
 
 module.exports = ProcessBuilder
\ No newline at end of file