diff --git a/src/read.c b/src/read.c
index 6a7124e..752ed52 100644
--- a/src/read.c
+++ b/src/read.c
@@ -297,7 +297,7 @@ AARU_EXPORT int32_t AARU_CALL aaruf_read_sector(void *context, const uint64_t se
         return AARUF_ERROR_NOT_AARUFORMAT;
     }
 
-    if(negative && sector_address > ctx->user_data_ddt_header.negative - 1)
+    if(negative && sector_address > ctx->user_data_ddt_header.negative)
     {
         FATAL("Sector address out of bounds");
 
@@ -868,7 +868,7 @@ AARU_EXPORT int32_t AARU_CALL aaruf_read_sector_long(void *context, const uint64
         return AARUF_ERROR_NOT_AARUFORMAT;
     }
 
-    if(negative && sector_address > ctx->user_data_ddt_header.negative - 1)
+    if(negative && sector_address > ctx->user_data_ddt_header.negative)
     {
         FATAL("Sector address out of bounds");
 
@@ -1509,7 +1509,7 @@ AARU_EXPORT int32_t AARU_CALL aaruf_read_sector_tag(const void *context, const u
         return AARUF_ERROR_NOT_AARUFORMAT;
     }
 
-    if(negative && sector_address > ctx->user_data_ddt_header.negative - 1)
+    if(negative && sector_address > ctx->user_data_ddt_header.negative)
     {
         FATAL("Sector address out of bounds");
 
diff --git a/src/write.c b/src/write.c
index 0a33efe..477c793 100644
--- a/src/write.c
+++ b/src/write.c
@@ -130,7 +130,7 @@ AARU_EXPORT int32_t AARU_CALL aaruf_write_sector(void *context, uint64_t sector_
         return AARUF_READ_ONLY;
     }
 
-    if(negative && sector_address > ctx->user_data_ddt_header.negative - 1)
+    if(negative && sector_address > ctx->user_data_ddt_header.negative)
     {
         FATAL("Sector address out of bounds");
 
@@ -569,7 +569,7 @@ AARU_EXPORT int32_t AARU_CALL aaruf_write_sector_long(void *context, uint64_t se
         return AARUF_READ_ONLY;
     }
 
-    if(negative && sector_address > ctx->user_data_ddt_header.negative - 1)
+    if(negative && sector_address > ctx->user_data_ddt_header.negative)
     {
         FATAL("Sector address out of bounds");
 
@@ -2101,7 +2101,7 @@ AARU_EXPORT int32_t AARU_CALL aaruf_write_sector_tag(void *context, const uint64
         return AARUF_READ_ONLY;
     }
 
-    if(negative && sector_address > ctx->user_data_ddt_header.negative - 1)
+    if(negative && sector_address > ctx->user_data_ddt_header.negative)
     {
         FATAL("Sector address out of bounds");