diff --git a/include/asm/main.h b/include/asm/main.h
index 8ea718a4..7fa446bb 100644
--- a/include/asm/main.h
+++ b/include/asm/main.h
@@ -26,8 +26,25 @@ extern void opt_Push(void);
 extern void opt_Pop(void);
 extern void opt_Parse(char *s);
 
+/*
+ * Used for errors that compromise the whole assembly process by affecting the
+ * folliwing code, potencially making the assembler generate errors caused by
+ * the first one and unrelated to the code that the assembler complains about.
+ * It is also used when the assembler goes into an invalid state (for example,
+ * when it fails to allocate memory).
+ */
 noreturn void fatalerror(const char *fmt, ...);
+/*
+ * Used for errors that make it impossible to assemble correctly, but don't
+ * affect the following code. The code will fail to assemble but the user will
+ * get a list of all errors at the end, making it easier to fix all of them at
+ * once.
+ */
 void yyerror(const char *fmt, ...);
+/*
+ * Used to warn the user about problems that don't prevent the generation of
+ * valid code.
+ */
 void warning(const char *fmt, ...);
 
 #define	YY_FATAL_ERROR fatalerror
diff --git a/src/asm/lexer.c b/src/asm/lexer.c
index f456636e..a650273e 100644
--- a/src/asm/lexer.c
+++ b/src/asm/lexer.c
@@ -535,7 +535,7 @@ yylex_ReadBracketedSymbol(char *dest, size_t index)
 	if (*pLexBuffer == '}')
 		pLexBuffer++;
 	else
-		yyerror("Missing }");
+		fatalerror("Missing }");
 
 	return length;
 }
@@ -601,7 +601,7 @@ yylex_ReadQuotedString()
 	if (*pLexBuffer == '"')
 		pLexBuffer++;
 	else
-		yyerror("Unterminated string");
+		fatalerror("Unterminated string");
 }
 
 ULONG
diff --git a/src/asm/output.c b/src/asm/output.c
index 4bc1ae9e..35961dc8 100644
--- a/src/asm/output.c
+++ b/src/asm/output.c
@@ -480,7 +480,8 @@ checksectionoverflow(ULONG delta_size)
 		/*
 		 * This check is here to trap broken code that generates
 		 * sections that are too big and to prevent the assembler from
-		 * generating huge object files.
+		 * generating huge object files or trying to allocate too much
+		 * memory.
 		 * The real check must be done at the linking stage.
 		 */
 		fatalerror("Section '%s' is too big (max size = 0x%X bytes).",