diff --git a/basicmbr.h b/basicmbr.h
index b809856..21f962e 100644
--- a/basicmbr.h
+++ b/basicmbr.h
@@ -34,6 +34,7 @@ struct TempMBR {
    struct MBRRecord partitions[4];
    uint16_t MBRSignature;
 }; // struct TempMBR
+#pragma pack ()
 
 // Possible states of the MBR
 enum MBRValidity {invalid, gpt, hybrid, mbr};
diff --git a/bsd.h b/bsd.h
index ffbe5cc..cbd3588 100644
--- a/bsd.h
+++ b/bsd.h
@@ -89,5 +89,6 @@ class BSDData {
       int GetNumParts(void);
       GPTPart AsGPT(int i); // Return BSD part. as GPT part.
 }; // struct MBRData
+#pragma pack ()
 
 #endif
diff --git a/gpt.h b/gpt.h
index 2d7a1ce..f4bf470 100644
--- a/gpt.h
+++ b/gpt.h
@@ -57,6 +57,7 @@ struct GPTHeader {
    uint32_t partitionEntriesCRC;
    unsigned char reserved2[GPT_RESERVED];
 }; // struct GPTHeader
+#pragma pack ()
 
 // Data in GPT format
 class GPTData {
diff --git a/mbrpart.h b/mbrpart.h
index f5892e7..0de365f 100644
--- a/mbrpart.h
+++ b/mbrpart.h
@@ -50,6 +50,7 @@ struct MBRRecord {
    uint32_t firstLBA; // see above
    uint32_t lengthLBA;
 }; // struct MBRRecord
+#pragma pack ()
 
 class MBRPart {
 protected: