diff --git a/src/arch/i386/prefix/libprefix.S b/src/arch/i386/prefix/libprefix.S
index 34eacb90..42189135 100644
--- a/src/arch/i386/prefix/libprefix.S
+++ b/src/arch/i386/prefix/libprefix.S
@@ -179,14 +179,14 @@ print_pci_busdevfn:
 	xchgb	%al, %ah
 	call	print_hex_byte
 	/* Print ":" */
-	movb	$':', %al
+	movb	$( ':' ), %al
 	call	print_character
 	/* Print device */
 	movb	%ah, %al
 	shrb	$3, %al
 	call	print_hex_byte
 	/* Print "." */
-	movb	$'.', %al
+	movb	$( '.' ), %al
 	call	print_character
 	/* Print function */
 	movb	%ah, %al
@@ -214,15 +214,15 @@ print_kill_line:
 	pushw	%ax
 	pushw	%cx
 	/* Print CR */
-	movb	$'\r', %al
+	movb	$( '\r' ), %al
 	call	print_character
 	/* Print 79 spaces */
-	movb	$' ', %al
+	movb	$( ' ' ), %al
 	movw	$79, %cx
 1:	call	print_character
 	loop	1b
 	/* Print CR */
-	movb	$'\r', %al
+	movb	$( '\r' ), %al
 	call	print_character
 	/* Restore registers and return */
 	popw	%cx
diff --git a/src/arch/i386/prefix/pxeprefix.S b/src/arch/i386/prefix/pxeprefix.S
index 3578fff7..575f4784 100644
--- a/src/arch/i386/prefix/pxeprefix.S
+++ b/src/arch/i386/prefix/pxeprefix.S
@@ -65,7 +65,7 @@ detect_pxenv:
 	movw	$10f, %si
 	call	print_message
 	call	print_segoff
-	movb	$',', %al
+	movb	$( ',' ), %al
 	call	print_character
 	jmp	99f
 	.section ".prefix.data", "aw", @progbits
@@ -103,7 +103,7 @@ detect_ppxe:
 	movw	$10f, %si
 	call	print_message
 	call	print_segoff
-	movb	$',', %al
+	movb	$( ',' ), %al
 	call	print_character
 	jmp	99f
 	.section ".prefix.data", "aw", @progbits
@@ -191,7 +191,7 @@ print_structure_information:
 	call	print_message
 	movw	undi_fbms_start, %ax
 	call	print_word
-	movb	$'-', %al
+	movb	$( '-' ), %al
 	call	print_character
 	movw	undi_fbms_end, %ax
 	call	print_word
@@ -334,7 +334,7 @@ print_segoff:
 	/* Print "<segment>:offset" */
 	movw	%es, %ax
 	call	print_hex_word
-	movb	$':', %al
+	movb	$( ':' ), %al
 	call	print_character
 	movw	%bx, %ax
 	call	print_hex_word
diff --git a/src/arch/i386/prefix/romprefix.S b/src/arch/i386/prefix/romprefix.S
index 2664e340..7d532375 100644
--- a/src/arch/i386/prefix/romprefix.S
+++ b/src/arch/i386/prefix/romprefix.S
@@ -175,10 +175,10 @@ init:
 	/* Fill in product name string, if possible */
 	movw	$prodstr_pci_id, %di
 	call	print_pci_busdevfn
-	movb	$' ', prodstr_separator
+	movb	$( ' ' ), prodstr_separator
 
 	/* Print segment address */
-	movb	$' ', %al
+	movb	$( ' ' ), %al
 	xorw	%di, %di
 	call	print_character
 	movw	%cs, %ax
@@ -201,7 +201,7 @@ init:
 	call	print_message
 	movb	%bh, %al
 	call	print_hex_nibble
-	movb	$'.', %al
+	movb	$( '.' ), %al
 	call	print_character
 	movb	%bl, %al
 	call	print_hex_byte
@@ -224,7 +224,7 @@ init:
 	cmpw	%bx, %ax
 	jbe	1f
 pci3_insane: /* PCI 3.0 with insane %gs value: print error and ignore %gs */
-	movb	$'!', %al
+	movb	$( '!' ), %al
 	call	print_character
 	movw	%gs, %ax
 	call	print_hex_word
@@ -332,7 +332,7 @@ got_pmm: /* PMM allocation succeeded */
 	movw	%dx, %ax
 	xorw	%di, %di
 	call	print_hex_word
-	movb	$'@', %al
+	movb	$( '@' ), %al
 	call	print_character
 	movw	%si, %ax
 	call	print_hex_byte
@@ -366,7 +366,7 @@ no_pmm:
 	 * loads us to a temporary location in low memory.  Will be a
 	 * no-op for lower PCI versions.
 	 */
-	movb	$' ', %al
+	movb	$( ' ' ), %al
 	xorw	%di, %di
 	call	print_character
 	movw	%gs, %ax