diff --git a/lang/diag.c b/lang/diag.c
index a95a8bb..7e2fc7b 100644
--- a/lang/diag.c
+++ b/lang/diag.c
@@ -8,6 +8,7 @@
 
 static const struct ivy_diag_class diag_classes[] = {
 	ERROR_CLASS(IVY_LANG_E_UNRECOGNISED_SYMBOL, "Unrecognised symbol"),
+	ERROR_CLASS(IVY_LANG_E_MISSING_WHITESPACE, "Missing whitespace"),
 	ERROR_CLASS(IVY_LANG_E_UNDEFINED_VARIABLE, "Undefined variable"),
 	ERROR_CLASS(
 		IVY_LANG_E_INCORRECT_INLINE_FOR_LOOP,
@@ -18,6 +19,9 @@ static const size_t nr_diag_classes = sizeof diag_classes / sizeof diag_classes[
 static const struct ivy_diag_msg diag_msg[] = {
 	MSG(IVY_LANG_MSG_UNKNOWN_SYMBOL_ENCOUNTERED,
             "encountered a symbol that is not part of the Ivy syntax."),
+	MSG(IVY_LANG_MSG_WHITESPACE_REQUIRED_AROUND_BINARY_OP,
+            "There must be a space between a binary operator and its "
+            "operands."),
 	MSG(IVY_LANG_MSG_ASSIGN_TO_UNDEFINED_VARIABLE,
             "cannot use modify-and-assign operator on an undefined variable."),
 	MSG(IVY_LANG_MSG_DO_UNEXPECTED_IN_INLINE_FOR,
diff --git a/lang/include/ivy/lang/diag.h b/lang/include/ivy/lang/diag.h
index e93dc8e..f26066e 100644
--- a/lang/include/ivy/lang/diag.h
+++ b/lang/include/ivy/lang/diag.h
@@ -8,14 +8,16 @@ struct ivy_diag_ctx;
 enum ivy_lang_diag_code {
 	IVY_LANG_E_NONE = 0,
 	IVY_LANG_E_UNRECOGNISED_SYMBOL,
+	IVY_LANG_E_MISSING_WHITESPACE,
 	IVY_LANG_E_UNDEFINED_VARIABLE,
 	IVY_LANG_E_INCORRECT_INLINE_FOR_LOOP,
 };
 
 enum ivy_lang_diag_msg {
 	IVY_LANG_MSG_NONE = 0,
-	IVY_LANG_MSG_ASSIGN_TO_UNDEFINED_VARIABLE,
 	IVY_LANG_MSG_UNKNOWN_SYMBOL_ENCOUNTERED,
+	IVY_LANG_MSG_WHITESPACE_REQUIRED_AROUND_BINARY_OP,
+	IVY_LANG_MSG_ASSIGN_TO_UNDEFINED_VARIABLE,
 	IVY_LANG_MSG_DO_UNEXPECTED_IN_INLINE_FOR,
 	IVY_LANG_MSG_PREVIOUS_EXPRESSION_IS_FOR_BODY,
 	IVY_LANG_MSG_DECLARE_GLOBAL_FOR_ASSIGNMENT,