diff --git a/src/asm/asmy.y b/src/asm/asmy.y
index 29dd9f01..c06d47e3 100644
--- a/src/asm/asmy.y
+++ b/src/asm/asmy.y
@@ -182,6 +182,10 @@ void	copyrept( void )
 		}
 	}
 
+	if (level != 0) {
+		fatalerror("Unterminated REPT block");
+	}
+
 	len=src-pCurrentBuffer->pBuffer-4;
 
 	src=pCurrentBuffer->pBuffer;
@@ -257,6 +261,10 @@ void	copymacro( void )
 		}
 	}
 
+	if (level != 0) {
+		fatalerror("Unterminated MACRO definition");
+	}
+
 	len=src-pCurrentBuffer->pBuffer-4;
 
 	src=pCurrentBuffer->pBuffer;
@@ -348,6 +356,10 @@ void	if_skip_to_else( void )
 		}
 	}
 
+	if (level != 0) {
+		fatalerror("Unterminated IF construct");
+	}
+
 	len=src-pCurrentBuffer->pBuffer;
 
 	yyskipbytes( len );
@@ -403,6 +415,10 @@ void	if_skip_to_endc( void )
 		}
 	}
 
+	if (level != 0) {
+		fatalerror("Unterminated IF construct");
+	}
+
 	len=src-pCurrentBuffer->pBuffer;
 
 	yyskipbytes( len );