diff --git a/include/asm/lexer.h b/include/asm/lexer.h
index 0f33c916..6f9d1fa1 100644
--- a/include/asm/lexer.h
+++ b/include/asm/lexer.h
@@ -30,6 +30,19 @@ static inline void lexer_SetStateAtEOL(struct LexerState *state)
 	lexerStateEOL = state;
 }
 
+extern char const *binDigits;
+extern char const *gfxDigits;
+
+static inline void lexer_SetBinDigits(char const *digits)
+{
+	binDigits = digits;
+}
+
+static inline void lexer_SetGfxDigits(char const *digits)
+{
+	gfxDigits = digits;
+}
+
 struct LexerState *lexer_OpenFile(char const *path);
 struct LexerState *lexer_OpenFileView(char *buf, size_t size, uint32_t lineNo);
 void lexer_RestartRept(uint32_t lineNo);
diff --git a/src/asm/fstack.c b/src/asm/fstack.c
index 0a8cf5f1..a464f436 100644
--- a/src/asm/fstack.c
+++ b/src/asm/fstack.c
@@ -336,7 +336,7 @@ char const *fstk_GetFileName(void)
 	int nbChars = snprintf(dest, remainingChars, __VA_ARGS__); \
 	\
 	if (nbChars >= remainingChars) \
-		fatalerror("File stack entry too large"); \
+		fatalerror("File stack entry too large\n"); \
 	remainingChars -= nbChars; \
 	dest += nbChars; \
 } while (0)
diff --git a/src/asm/lexer.c b/src/asm/lexer.c
index 15483226..762fa148 100644
--- a/src/asm/lexer.c
+++ b/src/asm/lexer.c
@@ -966,20 +966,26 @@ static void readFractionalPart(void)
 	yylval.nConstValue |= fractional * (yylval.nConstValue >= 0 ? 1 : -1);
 }
 
+char const *binDigits;
+
 static void readBinaryNumber(void)
 {
 	uint32_t value = 0;
 
-	dbgPrint("Reading binary number\n");
+	dbgPrint("Reading binary number with digits [%c,%c]\n", binDigits[0], binDigits[1]);
 	for (;;) {
 		int c = peek(0);
+		int bit;
 
-		/* TODO: handle `-b`'s dynamic chars */
-		if (c != '0' && c != '1')
+		if (c == binDigits[0])
+			bit = 0;
+		else if (c == binDigits[1])
+			bit = 1;
+		else
 			break;
-		if (value > (UINT32_MAX - (c - '0')) / 2)
+		if (value > (UINT32_MAX - bit) / 2)
 			warning(WARNING_LARGE_CONSTANT, "Integer constant is too large\n");
-		value = value * 2 + (c - '0');
+		value = value * 2 + bit;
 
 		shiftChars(1);
 	}
@@ -1019,19 +1025,29 @@ static void readHexNumber(void)
 	yylval.nConstValue = value;
 }
 
+char const *gfxDigits;
+
 static void readGfxConstant(void)
 {
 	uint32_t bp0 = 0, bp1 = 0;
 	uint8_t width = 0;
 
-	dbgPrint("Reading gfx constant\n");
+	dbgPrint("Reading gfx constant with digits [%c,%c,%c,%c]\n",
+		 gfxDigits[0], gfxDigits[1], gfxDigits[2], gfxDigits[3]);
 	for (;;) {
 		int c = peek(0);
+		uint32_t pixel;
 
-		/* TODO: handle `-g`'s dynamic chars */
-		if (c < '0' || c > '3')
+		if (c == gfxDigits[0])
+			pixel = 0;
+		else if (c == gfxDigits[1])
+			pixel = 1;
+		else if (c == gfxDigits[2])
+			pixel = 2;
+		else if (c == gfxDigits[3])
+			pixel = 3;
+		else
 			break;
-		uint8_t pixel = c - '0';
 
 		if (width < 8) {
 			bp0 = bp0 << 1 | (pixel & 1);
@@ -1531,7 +1547,7 @@ static int yylex_NORMAL(void)
 
 		case '%': /* Either a modulo, or a binary constant */
 			secondChar = peek(0);
-			if (secondChar != '0' && secondChar != '1')
+			if (secondChar != binDigits[0] && secondChar != binDigits[1])
 				return T_OP_MOD;
 
 			yylval.nConstValue = 0;
diff --git a/src/asm/main.c b/src/asm/main.c
index 4f264d36..c57b7fba 100644
--- a/src/asm/main.c
+++ b/src/asm/main.c
@@ -71,10 +71,11 @@ struct sOptionStackEntry {
 
 struct sOptionStackEntry *pOptionStack;
 
-void opt_SetCurrentOptions(struct sOptions *pOpt)
+void opt_SetCurrentOptions(struct sOptions *opt)
 {
-	/* TODO */
-	(void)pOpt;
+	CurrentOptions = *opt;
+	lexer_SetGfxDigits(CurrentOptions.gbgfx);
+	lexer_SetBinDigits(CurrentOptions.binary);
 }
 
 void opt_Parse(char *s)
diff --git a/test/asm/opt-b.asm b/test/asm/opt-b.asm
new file mode 100644
index 00000000..cd16ab38
--- /dev/null
+++ b/test/asm/opt-b.asm
@@ -0,0 +1,2 @@
+OPT b.X
+PRINTV %..X.X.X.
diff --git a/test/asm/opt-b.err b/test/asm/opt-b.err
new file mode 100644
index 00000000..e69de29b
diff --git a/test/asm/opt-b.out b/test/asm/opt-b.out
new file mode 100644
index 00000000..fce2ec6e
--- /dev/null
+++ b/test/asm/opt-b.out
@@ -0,0 +1 @@
+$2A
\ No newline at end of file
diff --git a/test/asm/opt-g.asm b/test/asm/opt-g.asm
new file mode 100644
index 00000000..5c165817
--- /dev/null
+++ b/test/asm/opt-g.asm
@@ -0,0 +1,2 @@
+OPT g.x0X
+PRINTV `.x.x0X0X
diff --git a/test/asm/opt-g.err b/test/asm/opt-g.err
new file mode 100644
index 00000000..e69de29b
diff --git a/test/asm/opt-g.out b/test/asm/opt-g.out
new file mode 100644
index 00000000..e0c24b67
--- /dev/null
+++ b/test/asm/opt-g.out
@@ -0,0 +1 @@
+$F55
\ No newline at end of file