diff --git a/src/variable.cpp b/src/variable.cpp
index d6eec9eeb3..4117c41da6 100644
--- a/src/variable.cpp
+++ b/src/variable.cpp
@@ -170,7 +170,8 @@ void Variable::set(int narg, char **arg)
   // doesn't matter if variable no longer exists
 
   if (strcmp(arg[1],"delete") == 0) {
-    if (narg != 2) error->all(FLERR,"Illegal variable command: expected 2 argument but found {}", narg);
+    if (narg != 2)
+      error->all(FLERR,"Illegal variable delete command: expected 2 arguments but found {}", narg);
     if (find(arg[0]) >= 0) remove(find(arg[0]));
     return;
 
diff --git a/unittest/commands/test_variables.cpp b/unittest/commands/test_variables.cpp
index cf124eeafd..2b1beddd48 100644
--- a/unittest/commands/test_variables.cpp
+++ b/unittest/commands/test_variables.cpp
@@ -197,11 +197,11 @@ TEST_F(VariableTest, CreateDelete)
     ASSERT_EQ(variable->internalstyle(variable->find("ten")), 1);
 
     TEST_FAILURE(".*ERROR: Illegal variable command.*", command("variable"););
-    TEST_FAILURE(".*ERROR: Illegal variable command.*", command("variable dummy index"););
-    TEST_FAILURE(".*ERROR: Illegal variable command.*", command("variable dummy delete xxx"););
-    TEST_FAILURE(".*ERROR: Illegal variable command.*", command("variable dummy loop -1"););
-    TEST_FAILURE(".*ERROR: Illegal variable command.*", command("variable dummy loop 10 1"););
-    TEST_FAILURE(".*ERROR: Illegal variable command.*", command("variable dummy xxxx"););
+    TEST_FAILURE(".*ERROR: Illegal variable index command.*", command("variable dummy index"););
+    TEST_FAILURE(".*ERROR: Illegal variable delete command: expected 2 arguments but found 3.*", command("variable dummy delete xxx"););
+    TEST_FAILURE(".*ERROR: Invalid variable loop argument: -1.*", command("variable dummy loop -1"););
+    TEST_FAILURE(".*ERROR: Illegal variable loop command.*", command("variable dummy loop 10 1"););
+    TEST_FAILURE(".*ERROR: Unknown variable keyword: xxx.*", command("variable dummy xxxx"););
     TEST_FAILURE(".*ERROR: Cannot redefine variable as a different style.*",
                  command("variable two string xxx"););
     TEST_FAILURE(".*ERROR: Cannot redefine variable as a different style.*",