diff --git a/public/app/plugins/datasource/prometheus/querybuilder/shared/OperationHeader.tsx b/public/app/plugins/datasource/prometheus/querybuilder/shared/OperationHeader.tsx
index 7ca2d4630d4..f6acf54caae 100644
--- a/public/app/plugins/datasource/prometheus/querybuilder/shared/OperationHeader.tsx
+++ b/public/app/plugins/datasource/prometheus/querybuilder/shared/OperationHeader.tsx
@@ -79,7 +79,16 @@ export const OperationHeader = React.memo<Props>(
                 if (value.value) {
                   // Operation should exist if it is selectable
                   const newDef = queryModeller.getOperationDef(value.value.id)!;
-                  let changedOp = { ...operation, id: value.value.id };
+
+                  // copy default params, and override with all current params
+                  const newParams = [...newDef.defaultParams];
+                  for (let i = 0; i < Math.min(operation.params.length, newParams.length); i++) {
+                    if (newDef.params[i].type === def.params[i].type) {
+                      newParams[i] = operation.params[i];
+                    }
+                  }
+
+                  const changedOp = { ...operation, params: newParams, id: value.value.id };
                   onChange(index, def.changeTypeHandler ? def.changeTypeHandler(changedOp, newDef) : changedOp);
                 }
               }}