diff --git a/reactos/ntoskrnl/io/iomgr/driver.c b/reactos/ntoskrnl/io/iomgr/driver.c
index 1264454e04b..c162bdb08dd 100644
--- a/reactos/ntoskrnl/io/iomgr/driver.c
+++ b/reactos/ntoskrnl/io/iomgr/driver.c
@@ -1403,9 +1403,19 @@ try_again:
     /* Loop all Major Functions */
     for (i = 0; i <= IRP_MJ_MAXIMUM_FUNCTION; i++)
     {
-        /* Set each function that was set to NULL to internal routine */
+        /*
+         * Make sure the driver didn't set any dispatch entry point to NULL!
+         * Doing so is illegal; drivers shouldn't touch entry points they
+         * do not implement.
+         */
+        ASSERT(DriverObject->MajorFunction[i] != NULL);
+
+        /* Check if it did so anyway */
 		if (!DriverObject->MajorFunction[i])
+        {
+            /* Fix it up */
             DriverObject->MajorFunction[i] = IopInvalidDeviceRequest;
+        }
     }
 
     /* Return the Status */
diff --git a/reactos/ntoskrnl/io/iomgr/iomdl.c b/reactos/ntoskrnl/io/iomgr/iomdl.c
index a5fcf71d814..c6ca981a8ac 100644
--- a/reactos/ntoskrnl/io/iomgr/iomdl.c
+++ b/reactos/ntoskrnl/io/iomgr/iomdl.c
@@ -29,6 +29,9 @@ IoAllocateMdl(IN PVOID VirtualAddress,
     ULONG Flags = 0;
     ULONG Size;
 
+    /* Make sure we got a valid length */
+    ASSERT(Length != 0);
+
     /* Fail if allocation is over 2GB */
     if (Length & 0x80000000) return NULL;
 
diff --git a/reactos/ntoskrnl/io/iomgr/irp.c b/reactos/ntoskrnl/io/iomgr/irp.c
index 1e81e205f84..e7e0fb1fe20 100644
--- a/reactos/ntoskrnl/io/iomgr/irp.c
+++ b/reactos/ntoskrnl/io/iomgr/irp.c
@@ -1134,6 +1134,9 @@ IofCallDriver(IN PDEVICE_OBJECT DeviceObject,
     PDRIVER_OBJECT DriverObject;
     PIO_STACK_LOCATION StackPtr;
 
+    /* Make sure this is a valid IRP */
+    ASSERT(Irp->Type == IO_TYPE_IRP);
+
     /* Get the Driver Object */
     DriverObject = DeviceObject->DriverObject;
 
diff --git a/reactos/ntoskrnl/mm/ARM3/contmem.c b/reactos/ntoskrnl/mm/ARM3/contmem.c
index bc1a18eb3da..c5565d2d8ec 100644
--- a/reactos/ntoskrnl/mm/ARM3/contmem.c
+++ b/reactos/ntoskrnl/mm/ARM3/contmem.c
@@ -173,8 +173,13 @@ MiAllocateContiguousMemory(IN SIZE_T NumberOfBytes,
 {
     PVOID BaseAddress;
     PFN_NUMBER SizeInPages;
-    MI_PFN_CACHE_ATTRIBUTE CacheAttribute;   
+    MI_PFN_CACHE_ATTRIBUTE CacheAttribute;
+
+    //
+    // Verify count and cache type
+    //
     ASSERT(NumberOfBytes != 0);
+    ASSERT(CacheType <= MmWriteCombined);
     
     //
     // Compute size requested
@@ -352,7 +357,12 @@ MmAllocateContiguousMemorySpecifyCache(IN SIZE_T NumberOfBytes,
                                        IN MEMORY_CACHING_TYPE CacheType OPTIONAL)
 {
     PFN_NUMBER LowestPfn, HighestPfn, BoundaryPfn;
-    ASSERT (NumberOfBytes != 0);
+
+    //
+    // Verify count and cache type
+    //
+    ASSERT(NumberOfBytes != 0);
+    ASSERT(CacheType <= MmWriteCombined);
     
     //
     // Convert the lowest address into a PFN
@@ -396,7 +406,12 @@ MmAllocateContiguousMemory(IN ULONG NumberOfBytes,
                            IN PHYSICAL_ADDRESS HighestAcceptableAddress)
 {
     PFN_NUMBER HighestPfn;
-    
+
+    //
+    // Verify byte count
+    //
+    ASSERT(NumberOfBytes != 0);
+
     //
     // Convert and normalize the highest address into a PFN
     //
diff --git a/reactos/ntoskrnl/mm/ARM3/iosup.c b/reactos/ntoskrnl/mm/ARM3/iosup.c
index 5d3452b2ad4..7ea829711c3 100644
--- a/reactos/ntoskrnl/mm/ARM3/iosup.c
+++ b/reactos/ntoskrnl/mm/ARM3/iosup.c
@@ -57,7 +57,22 @@ MmMapIoSpace(IN PHYSICAL_ADDRESS PhysicalAddress,
     PMMPFN Pfn1 = NULL;
     MI_PFN_CACHE_ATTRIBUTE CacheAttribute;
     BOOLEAN IsIoMapping;
-    
+
+    //
+    // Must be called with a non-zero count
+    //
+    ASSERT(NumberOfBytes != 0);
+
+    //
+    // Make sure the upper bits are 0 if this system
+    // can't describe more than 4 GB of physical memory.
+    // FIXME: This doesn't respect PAE, but we currently don't
+    // define a PAE build flag since there is no such build.
+    //
+#if !defined(_M_AMD64)
+    ASSERT(PhysicalAddress.HighPart == 0);
+#endif
+
     //
     // Normalize and validate the caching attributes
     //
diff --git a/reactos/ntoskrnl/mm/ARM3/mdlsup.c b/reactos/ntoskrnl/mm/ARM3/mdlsup.c
index 596fef88afb..0076759380f 100644
--- a/reactos/ntoskrnl/mm/ARM3/mdlsup.c
+++ b/reactos/ntoskrnl/mm/ARM3/mdlsup.c
@@ -507,8 +507,13 @@ MmUnmapLockedPages(IN PVOID BaseAddress,
         // Get the PTE
         //
         PointerPte = MiAddressToPte(BaseAddress);
+
+        //
+        // This should be a resident system PTE
+        //
         ASSERT(PointerPte >= MmSystemPtesStart[SystemPteSpace]);
         ASSERT(PointerPte <= MmSystemPtesEnd[SystemPteSpace]);
+        ASSERT(PointerPte->u.Hard.Valid == 1);
         
         //
         // Check if the caller wants us to free advanced pages
@@ -715,7 +720,7 @@ MmProbeAndLockPages(IN PMDL Mdl,
     //
     // Sanity check
     //
-    ASSERT(MdlPages = (PPFN_NUMBER)(Mdl + 1));
+    ASSERT(MdlPages == (PPFN_NUMBER)(Mdl + 1));
     
     //
     // Check what kind of operation this is