--- a/dom/canvas/WebGL2ContextUniforms.cpp
+++ b/dom/canvas/WebGL2ContextUniforms.cpp
@@ -167,16 +167,21 @@ WebGL2Context::GetActiveUniforms(JSConte
         return;
 
     if (!ValidateUniformEnum(this, pname, funcName))
         return;
 
     if (!ValidateObject("getActiveUniforms: program", program))
         return;
 
+    if (!program.IsLinked()) {
+        ErrorInvalidOperation("%s: `program` must be linked.", funcName);
+        return;
+    }
+
     const auto& numActiveUniforms = program.LinkInfo()->uniforms.size();
     for (const auto& curIndex : uniformIndices) {
         if (curIndex >= numActiveUniforms) {
             ErrorInvalidValue("%s: Too-large active uniform index queried.", funcName);
             return;
         }
     }