diff --git a/doc/upx.pod b/doc/upx.pod
index 3beaf419..0d03ffd8 100644
--- a/doc/upx.pod
+++ b/doc/upx.pod
@@ -138,6 +138,9 @@ B<--help>: prints the help
 
 B<--version>: print the version of B<UPX>
 
+B<--exact>: when compressing, require to be able to get a byte-identical file
+after decompression with option B<-d>
+
 [ ...to be written... - type `B<upx --help>' for now ]
 
 
diff --git a/src/except.cpp b/src/except.cpp
index 4f3645bc..1295001a 100644
--- a/src/except.cpp
+++ b/src/except.cpp
@@ -85,6 +85,11 @@ void throwCantPack(const char *msg)
         throw CantUnpackException(msg);
 }
 
+void throwCantPackExact()
+{
+    throwCantPack("option '--exact' does not work with this file");
+}
+
 void throwFilterException()
 {
     throwCantPack("filter problem");
diff --git a/src/except.h b/src/except.h
index 8c159d5b..e1d8dcba 100644
--- a/src/except.h
+++ b/src/except.h
@@ -208,6 +208,7 @@ public:
 #endif
 
 void throwCantPack(const char *msg) NORET;
+void throwCantPackExact() NORET;
 void throwUnknownExecutableFormat(const char *msg = NULL, bool warn = false) NORET;
 void throwNotCompressible(const char *msg = NULL) NORET;
 void throwAlreadyPacked(const char *msg = NULL) NORET;
diff --git a/src/main.cpp b/src/main.cpp
index eddb4cd0..99c77ed1 100644
--- a/src/main.cpp
+++ b/src/main.cpp
@@ -643,6 +643,9 @@ static int do_option(int optc, const char *arg)
         opt->all_methods = true;
         opt->method = -1;
         break;
+    case 525:                               // --exact
+        opt->exact = true;
+        break;
     // compression runtime parameters
     case 801:
         getoptvar(&opt->crp.crp_ucl.c_flags, 0, 3, arg);
@@ -918,6 +921,7 @@ static const struct mfx_option longopts[] =
     // compression settings
     {"all-filters",      0x10, 0, 523},
     {"all-methods",      0x10, 0, 524},
+    {"exact",            0x10, 0, 525},     // user requires byte-identical decompression
     {"filter",           0x31, 0, 521},     // --filter=
     {"no-filter",        0x10, 0, 522},
     {"small",            0x10, 0, 520},
@@ -1051,6 +1055,9 @@ static const struct mfx_option longopts[] =
     {"mono",             0x10, 0, 513},
     {"color",            0x10, 0, 514},
 
+    // compression settings
+    {"exact",            0x10, 0, 525},     // user requires byte-identical decompression
+
     // compression runtime parameters
 
     // win32/pe
@@ -1412,6 +1419,8 @@ int __acc_cdecl_main main(int argc, char *argv[])
         // invalidate compression options
         opt->method = 0;
         opt->level = 0;
+        opt->exact = 0;
+        opt->small = 0;
         opt->crp.reset();
     }
 
diff --git a/src/options.h b/src/options.h
index 735c37a9..bbf37363 100644
--- a/src/options.h
+++ b/src/options.h
@@ -53,6 +53,7 @@ struct options_t {
     bool all_methods_use_lzma;
     bool all_filters;       // try all available filters ?
     bool no_filter;         // force no filter
+    bool exact;             // user requires byte-identical decompression
 
     // other options
     int backup;
diff --git a/src/p_tos.cpp b/src/p_tos.cpp
index 47bcee3c..9eb9bb30 100644
--- a/src/p_tos.cpp
+++ b/src/p_tos.cpp
@@ -439,6 +439,8 @@ void PackTos::pack(OutputFile *fo)
     t = i_text + i_data;
     fi->readx(ibuf,t);
     // skip symbols
+    if (i_sym && opt->exact)
+        throwCantPackExact();
     fi->seek(i_sym,SEEK_CUR);
     // read relocations + overlay
     overlay = file_size - (FH_SIZE + i_text + i_data + i_sym);