diff --git a/lib/fast486/fpu.c b/lib/fast486/fpu.c
index a73e079ff75..a4a35116066 100644
--- a/lib/fast486/fpu.c
+++ b/lib/fast486/fpu.c
@@ -35,8 +35,17 @@
 
 FAST486_OPCODE_HANDLER(Fast486FpuOpcodeD8)
 {
+    UCHAR Function;
+
     FPU_CHECK();
 
+    /* Fetch the function number */
+    if (!Fast486FetchByte(State, &Function))
+    {
+        /* Exception occurred */
+        return FALSE;
+    }
+
 #ifndef FAST486_NO_FPU
     // TODO: NOT IMPLEMENTED
     UNIMPLEMENTED;
@@ -50,8 +59,17 @@ FAST486_OPCODE_HANDLER(Fast486FpuOpcodeD8)
 
 FAST486_OPCODE_HANDLER(Fast486FpuOpcodeD9)
 {
+    UCHAR Function;
+
     FPU_CHECK();
 
+    /* Fetch the function number */
+    if (!Fast486FetchByte(State, &Function))
+    {
+        /* Exception occurred */
+        return FALSE;
+    }
+
 #ifndef FAST486_NO_FPU
     // TODO: NOT IMPLEMENTED
     UNIMPLEMENTED;
@@ -65,8 +83,17 @@ FAST486_OPCODE_HANDLER(Fast486FpuOpcodeD9)
 
 FAST486_OPCODE_HANDLER(Fast486FpuOpcodeDA)
 {
+    UCHAR Function;
+
     FPU_CHECK();
 
+    /* Fetch the function number */
+    if (!Fast486FetchByte(State, &Function))
+    {
+        /* Exception occurred */
+        return FALSE;
+    }
+
 #ifndef FAST486_NO_FPU
     // TODO: NOT IMPLEMENTED
     UNIMPLEMENTED;
@@ -80,8 +107,17 @@ FAST486_OPCODE_HANDLER(Fast486FpuOpcodeDA)
 
 FAST486_OPCODE_HANDLER(Fast486FpuOpcodeDB)
 {
+    UCHAR Function;
+
     FPU_CHECK();
 
+    /* Fetch the function number */
+    if (!Fast486FetchByte(State, &Function))
+    {
+        /* Exception occurred */
+        return FALSE;
+    }
+
 #ifndef FAST486_NO_FPU
     // TODO: NOT IMPLEMENTED
     UNIMPLEMENTED;
@@ -95,8 +131,17 @@ FAST486_OPCODE_HANDLER(Fast486FpuOpcodeDB)
 
 FAST486_OPCODE_HANDLER(Fast486FpuOpcodeDC)
 {
+    UCHAR Function;
+
     FPU_CHECK();
 
+    /* Fetch the function number */
+    if (!Fast486FetchByte(State, &Function))
+    {
+        /* Exception occurred */
+        return FALSE;
+    }
+
 #ifndef FAST486_NO_FPU
     // TODO: NOT IMPLEMENTED
     UNIMPLEMENTED;
@@ -110,8 +155,17 @@ FAST486_OPCODE_HANDLER(Fast486FpuOpcodeDC)
 
 FAST486_OPCODE_HANDLER(Fast486FpuOpcodeDD)
 {
+    UCHAR Function;
+
     FPU_CHECK();
 
+    /* Fetch the function number */
+    if (!Fast486FetchByte(State, &Function))
+    {
+        /* Exception occurred */
+        return FALSE;
+    }
+
 #ifndef FAST486_NO_FPU
     // TODO: NOT IMPLEMENTED
     UNIMPLEMENTED;
@@ -125,8 +179,17 @@ FAST486_OPCODE_HANDLER(Fast486FpuOpcodeDD)
 
 FAST486_OPCODE_HANDLER(Fast486FpuOpcodeDE)
 {
+    UCHAR Function;
+
     FPU_CHECK();
 
+    /* Fetch the function number */
+    if (!Fast486FetchByte(State, &Function))
+    {
+        /* Exception occurred */
+        return FALSE;
+    }
+
 #ifndef FAST486_NO_FPU
     // TODO: NOT IMPLEMENTED
     UNIMPLEMENTED;
@@ -140,8 +203,17 @@ FAST486_OPCODE_HANDLER(Fast486FpuOpcodeDE)
 
 FAST486_OPCODE_HANDLER(Fast486FpuOpcodeDF)
 {
+    UCHAR Function;
+
     FPU_CHECK();
 
+    /* Fetch the function number */
+    if (!Fast486FetchByte(State, &Function))
+    {
+        /* Exception occurred */
+        return FALSE;
+    }
+
 #ifndef FAST486_NO_FPU
     // TODO: NOT IMPLEMENTED
     UNIMPLEMENTED;