diff --git a/code/vqa.cpp b/code/vqa.cpp
index bb892ddd4..ad4006de3 100644
--- a/code/vqa.cpp
+++ b/code/vqa.cpp
@@ -299,16 +299,16 @@ long VQAClass::CacheHandler(long action, void * buffer, long nbytes)
 			break;
 
 		case VQACMD_SEEK:
-			switch ((int)(intptr_t)buffer) {
-				case 1:
+			switch (VQA_DecodeSeekOrigin(buffer)) {
+				case SEEK_CUR:
 					Cache.file_buffer_pos += nbytes;
 					rc = 0;
 					break;
-				case 0:
+				case SEEK_SET:
 					Cache.file_buffer_pos = nbytes;
 					rc = 0;
 					break;
-				case 2:
+				case SEEK_END:
 					Cache.file_buffer_pos = Cache.file_size - nbytes - 1;
 					rc = 0;
 					break;
@@ -846,26 +846,25 @@ long VQAClass::CCFileHandler(long action, void * buffer, long nbytes)
 			break;
 
 		/*
-		**	VQACMD_SEEK asks that you perform a seek relative to the current
-		**	position. NBytes is a signed number, indicating seek direction
-		** (positive for forward, negative for backward). Buffer has no meaning
-		**	here.
+		**	VQACMD_SEEK asks that you perform a seek from the origin Buffer
+		**	names, which is a SEEK_SET, SEEK_CUR or SEEK_END value cast to a
+		**	pointer. NBytes is the signed offset from that origin.
 		**
 		**	Any error code returned will be remapped by VQA library into
 		**	VQAERR_SEEK.
 		*/
 		case VQACMD_SEEK:
-			error = (FileHandle.Seek(nbytes, (int)(intptr_t)buffer) == 0);
+			error = (FileHandle.Seek(nbytes, VQA_DecodeSeekOrigin(buffer)) == 0);
 			break;
 
 		case VQACMD_SEEKPEEK:
 			if (nbytes > 0) {
-				error = FileHandle.Seek(nbytes - sizeof(tmp), (int)(intptr_t)buffer) == 0;
+				error = FileHandle.Seek(nbytes - sizeof(tmp), VQA_DecodeSeekOrigin(buffer)) == 0;
 				if (error == 0) {
 					error = FileHandle.Read(&tmp, sizeof(tmp)) != sizeof(tmp);
 				}
 			} else {
-				error = FileHandle.Seek(nbytes, (int)(intptr_t)buffer) == 0;
+				error = FileHandle.Seek(nbytes, VQA_DecodeSeekOrigin(buffer)) == 0;
 				if (error == 0) {
 					error = FileHandle.Read(&tmp, sizeof(tmp)) != sizeof(tmp);
 					if (error == 0) {
@@ -973,26 +972,25 @@ long VQAClass::MixFileHandler(long action, void * buffer, long nbytes)
 			break;
 
 		/*
-		**	VQACMD_SEEK asks that you perform a seek relative to the current
-		**	position. NBytes is a signed number, indicating seek direction
-		** (positive for forward, negative for backward). Buffer has no meaning
-		**	here.
+		**	VQACMD_SEEK asks that you perform a seek from the origin Buffer
+		**	names, which is a SEEK_SET, SEEK_CUR or SEEK_END value cast to a
+		**	pointer. NBytes is the signed offset from that origin.
 		**
 		**	Any error code returned will be remapped by VQA library into
 		**	VQAERR_SEEK.
 		*/
 		case VQACMD_SEEK:
-			error = (FileHandle.Seek(nbytes, (int)(intptr_t)buffer) == 0);
+			error = (FileHandle.Seek(nbytes, VQA_DecodeSeekOrigin(buffer)) == 0);
 			break;
 
 		case VQACMD_SEEKPEEK:
 			if (nbytes > 0) {
-				error = FileHandle.Seek(nbytes - sizeof(tmp), (int)(intptr_t)buffer) == 0;
+				error = FileHandle.Seek(nbytes - sizeof(tmp), VQA_DecodeSeekOrigin(buffer)) == 0;
 				if (error == 0) {
 					error = FileHandle.Read(&tmp, sizeof(tmp)) != sizeof(tmp);
 				}
 			} else {
-				error = FileHandle.Seek(nbytes, (int)(intptr_t)buffer) == 0;
+				error = FileHandle.Seek(nbytes, VQA_DecodeSeekOrigin(buffer)) == 0;
 				if (error == 0) {
 					error = FileHandle.Read(&tmp, sizeof(tmp)) != sizeof(tmp);
 					if (error == 0) {
diff --git a/code/vqalib/dstream.cpp b/code/vqalib/dstream.cpp
index 456462e0f..e38527cf2 100644
--- a/code/vqalib/dstream.cpp
+++ b/code/vqalib/dstream.cpp
@@ -89,31 +89,30 @@ intptr_t __cdecl Disk_VQA_Stream_Handler(VQAHandle *vqa, long action, void *buff
 			error = 1;
 			break;
 
-		/* VQACMD_SEEK asks that you perform a seek relative to the current
-		 * position. NBytes is a signed number, indicating seek direction
-		 * (positive for forward, negative for backward). Buffer has no meaning
-		 * here.
+		/* VQACMD_SEEK asks that you perform a seek from the origin Buffer
+		 * names, which is a SEEK_SET, SEEK_CUR or SEEK_END value cast to a
+		 * pointer. NBytes is the signed offset from that origin.
 		 *
 		 * Any error code returned will be remapped by VQA library into
 		 * VQAERR_SEEK.
 		 */
 		case VQACMD_SEEK:
-			error = (lseek(fh, nbytes, (int)(intptr_t)buffer) == -1);
+			error = (lseek(fh, nbytes, VQA_DecodeSeekOrigin(buffer)) == -1);
 			break;
 
 		case VQACMD_SEEKPEEK:
 			if (nbytes > 0) {
-				error = lseek(fh, nbytes - 1, (int)(intptr_t)buffer) == -1;
+				error = lseek(fh, nbytes - 1, VQA_DecodeSeekOrigin(buffer)) == -1;
 				if (error == 0) {
 					error = read(fh, &temp, 1) != 1;
 				}
 			} else {
-				error = lseek(fh, nbytes, (int)(intptr_t)buffer) == -1;
+				error = lseek(fh, nbytes, VQA_DecodeSeekOrigin(buffer)) == -1;
 				if (error == 0) {
 					error = read(fh, &temp, 1) != 1;
 				}
 				if (error == 0) {
-					error = lseek(fh, -1, 1) == -1;
+					error = lseek(fh, -1, SEEK_CUR) == -1;
 				}
 			}
 			break;
@@ -186,24 +185,23 @@ intptr_t __cdecl Memory_VQA_Stream_Handler(VQAHandle *vqa, long action, void *bu
 			error = 1;
 			break;
 
-		/* VQACMD_SEEK asks that you perform a seek relative to the current
-		 * position. NBytes is a signed number, indicating seek direction
-		 * (positive for forward, negative for backward). Buffer has no meaning
-		 * here.
+		/* VQACMD_SEEK asks that you perform a seek from the origin Buffer
+		 * names, which is a SEEK_SET, SEEK_CUR or SEEK_END value cast to a
+		 * pointer. NBytes is the signed offset from that origin.
 		 *
 		 * Any error code returned will be remapped by VQA library into
 		 * VQAERR_SEEK.
 		 */
 		case VQACMD_SEEK:
 		case VQACMD_SEEKPEEK:
-			switch ((intptr_t)buffer) {
+			switch (VQA_DecodeSeekOrigin(buffer)) {
 
-				case 1:
+				case SEEK_CUR:
 					cache->Offset += nbytes;
 					error = 0;
 					break;
 
-				case 0:
+				case SEEK_SET:
 					p = cache->FileOffset;
 					if (nbytes >= p) {
 						cache->Offset = nbytes - p;
diff --git a/code/vqalib/loader.cpp b/code/vqalib/loader.cpp
index 63200ec69..fb05d1047 100644
--- a/code/vqalib/loader.cpp
+++ b/code/vqalib/loader.cpp
@@ -260,7 +260,7 @@ long VQA_LoadFrame(VQAHandleP *vqap, long flags)
 
 				if (tocache > 0) {
 					if (config->StreamHandler != Memory_VQA_Stream_Handler) {
-						config->StreamHandler((VQAHandle *)vqap, VQACMD_SEEK, NULL, foffset);
+						config->StreamHandler((VQAHandle *)vqap, VQACMD_SEEK, (void *)SEEK_SET, foffset);
 					}
 					if (config->StreamHandler((VQAHandle *)vqap, VQACMD_READ, &cache->Ptr[cache->Offset], tocache)) {
 						return -4;
@@ -1074,7 +1074,7 @@ long VQA_SeekLoop(VQAHandleP *vqap, long framenum, long flags)
 			needs_seek = true;
 		}
 		cache->Offset = 0;
-	} else if (vqap->Config.StreamHandler((VQAHandle *)vqap, VQACMD_SEEK, 0, VQAFRAME_OFFSET(foff[framenum])) != 0) {
+	} else if (vqap->Config.StreamHandler((VQAHandle *)vqap, VQACMD_SEEK, (void *)SEEK_SET, VQAFRAME_OFFSET(foff[framenum])) != 0) {
 		return(VQAERR_SEEK);
 	}
 
@@ -1083,7 +1083,7 @@ long VQA_SeekLoop(VQAHandleP *vqap, long framenum, long flags)
 	}
 
 	if (rc == VQAERR_NONE) {
-		if (needs_seek && vqap->Config.StreamHandler((VQAHandle *)vqap, VQACMD_SEEKPEEK, 0, cache->FileOffset + cache->Bytes) != 0) {
+		if (needs_seek && vqap->Config.StreamHandler((VQAHandle *)vqap, VQACMD_SEEKPEEK, (void *)SEEK_SET, cache->FileOffset + cache->Bytes) != 0) {
 			return(VQAERR_SEEK);
 		}
 	}
@@ -1826,7 +1826,7 @@ long Load_VQF(VQAHandleP *vqap, unsigned long frame_iffsize, char flags)
 
 		/* Skip any unknown chunks. */
 		if (skip == true) {
-			if (vqap->Config.StreamHandler((VQAHandle *)vqap, VQACMD_SEEK, (void *)1, PADSIZE(iffsize))) {
+			if (vqap->Config.StreamHandler((VQAHandle *)vqap, VQACMD_SEEK, (void *)SEEK_CUR, PADSIZE(iffsize))) {
 				return(VQAERR_SEEK);
 			}
 		}
diff --git a/code/vqalib/vqaplay.h b/code/vqalib/vqaplay.h
index 268e7fb24..3447bb396 100644
--- a/code/vqalib/vqaplay.h
+++ b/code/vqalib/vqaplay.h
@@ -366,6 +366,15 @@ typedef struct _VQAHandle {
 #define VQACMD_SEEKPEEK 8
 #define VQACMD_SIZE     9
 
+/* VQACMD_SEEK and VQACMD_SEEKPEEK carry the seek origin in Buffer rather
+ * than a pointer. It comes back at pointer width before narrowing to the
+ * int origin that lseek and FileClass::Seek take.
+ */
+inline int VQA_DecodeSeekOrigin(void *buffer)
+{
+	return (int)(std::intptr_t)buffer;
+}
+
 #define VQAMEM_0		0
 #define VQAMEM_1		1
 #define VQAMEM_ALLOC	2