diff --git a/src/radeon_atombios.c b/src/radeon_atombios.c
index 20aa722..03c7a67 100644
--- a/src/radeon_atombios.c
+++ b/src/radeon_atombios.c
@@ -654,12 +654,18 @@ rhdAtomVramInfoQuery(atomBiosHandlePtr handle, AtomBiosRequestID func,
 
     switch (func) {
 	case GET_FW_FB_START:
-	    *val = le32_to_cpu(atomDataPtr->VRAM_UsageByFirmware
-			       ->asFirmwareVramReserveInfo[0].ulStartAddrUsedByFirmware);
+	    if (atomDataPtr->VRAM_UsageByFirmware)
+		*val = le32_to_cpu(atomDataPtr->VRAM_UsageByFirmware
+				   ->asFirmwareVramReserveInfo[0].ulStartAddrUsedByFirmware);
+	    else
+		return ATOM_NOT_IMPLEMENTED;
 	    break;
 	case GET_FW_FB_SIZE:
-	    *val =  le16_to_cpu(atomDataPtr->VRAM_UsageByFirmware
-				->asFirmwareVramReserveInfo[0].usFirmwareUseInKb);
+	    if (atomDataPtr->VRAM_UsageByFirmware)
+		*val =  le16_to_cpu(atomDataPtr->VRAM_UsageByFirmware
+				    ->asFirmwareVramReserveInfo[0].usFirmwareUseInKb);
+	    else
+		return ATOM_NOT_IMPLEMENTED;
 	    break;
 	default:
 	    return ATOM_NOT_IMPLEMENTED;