diff --git a/src/MIDI.cpp b/src/MIDI.cpp
index c117d5a..9d53668 100644
--- a/src/MIDI.cpp
+++ b/src/MIDI.cpp
@@ -55,7 +55,7 @@ unsigned encodeSysEx(const byte* inData, byte* outSysEx, unsigned inLength)
         const byte msb  = data >> 7;
         const byte body = data & 0x7f;
 
-        outSysEx[0] |= (msb << count);
+        outSysEx[0] |= (msb << (6 - count));
         outSysEx[1 + count] = body;
 
         if (count++ == 6)
@@ -84,17 +84,20 @@ unsigned decodeSysEx(const byte* inSysEx, byte* outData, unsigned inLength)
 {
     unsigned count  = 0;
     byte msbStorage = 0;
+    byte byteIndex  = 0;
 
     for (unsigned i = 0; i < inLength; ++i)
     {
         if ((i % 8) == 0)
         {
             msbStorage = inSysEx[i];
+            byteIndex  = 6;
         }
         else
         {
-            outData[count++] = inSysEx[i] | ((msbStorage & 1) << 7);
-            msbStorage >>= 1;
+            const byte body = inSysEx[i];
+            const byte msb  = ((msbStorage >> byteIndex--) & 1) << 7;
+            outData[count++] = msb | body;
         }
     }
     return count;
diff --git a/test/unit-tests/CMakeLists.txt b/test/unit-tests/CMakeLists.txt
index a9bcb79..a77c826 100644
--- a/test/unit-tests/CMakeLists.txt
+++ b/test/unit-tests/CMakeLists.txt
@@ -3,6 +3,7 @@ project(unit-tests)
 include_directories(
     ${unit-tests_SOURCE_DIR}
     ${gtest_SOURCE_DIR}/include
+    ${gmock_SOURCE_DIR}/include
 )
 
 add_executable(unit-tests
@@ -13,10 +14,12 @@ add_executable(unit-tests
 
     tests/unit-tests_MidiMessage.cpp
     tests/unit-tests_Settings.cpp
+    tests/unit-tests_SysExCodec.cpp
 )
 
 target_link_libraries(unit-tests
     gtest
+    gmock
     midi
     test-mocks
 )
diff --git a/test/unit-tests/tests/unit-tests_SysExCodec.cpp b/test/unit-tests/tests/unit-tests_SysExCodec.cpp
new file mode 100644
index 0000000..f5c6335
--- /dev/null
+++ b/test/unit-tests/tests/unit-tests_SysExCodec.cpp
@@ -0,0 +1,103 @@
+#include "unit-tests.h"
+#include <src/MIDI.h>
+
+BEGIN_MIDI_NAMESPACE
+
+END_MIDI_NAMESPACE
+
+// -----------------------------------------------------------------------------
+
+BEGIN_UNNAMED_NAMESPACE
+
+using namespace testing;
+
+TEST(SysExCodec, Encoder)
+{
+    // ASCII content
+    {
+        const byte input[] = "Hello, World!";
+        byte buffer[32];
+        memset(buffer, 0, 32 * sizeof(byte));
+        const unsigned encodedSize = midi::encodeSysEx(input, buffer, 13);
+        EXPECT_EQ(encodedSize, 15);
+        const byte expected[32] = {
+            0, 'H', 'e', 'l', 'l', 'o', ',', ' ',
+            0, 'W', 'o', 'r', 'l', 'd', '!', 0,
+            0, 0, 0, 0, 0, 0, 0, 0,
+            0, 0, 0, 0, 0, 0, 0, 0,
+        };
+        EXPECT_THAT(buffer, Each(Le(0x7f))); // All elements are <= 127
+        EXPECT_THAT(buffer, ContainerEq(expected));
+    }
+    // Non-ASCII content
+    {
+        const byte input[] = {
+            182, 236, 167, 177, 61, 91, 120,    // 01111000 -> 120
+            107, 94, 209, 87, 94                // 000100xx -> 16
+        };
+        byte buffer[32];
+        memset(buffer, 0, 32 * sizeof(byte));
+        const unsigned encodedSize = midi::encodeSysEx(input, buffer, 12);
+        EXPECT_EQ(encodedSize, 14);
+        const byte expected[32] = {
+        //  MSB    Data
+            120,   54, 108, 39, 49, 61, 91, 120,
+            16,    107, 94, 81, 87, 94, 0,  0,
+            0, 0, 0, 0, 0, 0, 0, 0,
+            0, 0, 0, 0, 0, 0, 0, 0,
+        };
+        EXPECT_THAT(buffer, Each(Le(0x7f))); // All elements are <= 127
+        EXPECT_THAT(buffer, ContainerEq(expected));
+    }
+}
+
+TEST(SysExCodec, Decoder)
+{
+    // ASCII content
+    {
+        const byte input[] = {
+            0, 'H', 'e', 'l', 'l', 'o', ',', ' ',
+            0, 'W', 'o', 'r', 'l', 'd', '!',
+        };
+        byte buffer[32];
+        memset(buffer, 0, 32 * sizeof(byte));
+        const unsigned decodedSize = midi::decodeSysEx(input, buffer, 15);
+        EXPECT_EQ(decodedSize, 13);
+        const byte expected[32] = {
+            'H', 'e', 'l', 'l', 'o', ',', ' ', 'W',
+            'o', 'r', 'l', 'd', '!', 0, 0, 0,
+            0, 0, 0, 0, 0, 0, 0, 0,
+            0, 0, 0, 0, 0, 0, 0, 0,
+        };
+        EXPECT_THAT(buffer, Each(Le(0x7f))); // All elements are <= 127
+        EXPECT_THAT(buffer, ContainerEq(expected));
+    }
+    // Non-ASCII content
+    {
+        const byte input[] = {
+        //  MSB    Data
+            120,   54, 108, 39, 49, 61, 91, 120,
+            16,    107, 94, 81, 87, 94,
+        };
+        byte buffer[32];
+        memset(buffer, 0, 32 * sizeof(byte));
+        const unsigned encodedSize = midi::decodeSysEx(input, buffer, 14);
+        EXPECT_EQ(encodedSize, 12);
+        const byte expected[32] = {
+            182, 236, 167, 177, 61, 91, 120,
+            107, 94, 209, 87, 94, 0, 0,
+            0, 0, 0, 0, 0, 0, 0,
+            0, 0, 0, 0, 0, 0, 0,
+            0, 0, 0, 0
+        };
+        EXPECT_THAT(input,  Each(Le(0x7f))); // All elements are <= 127
+        EXPECT_THAT(buffer, ContainerEq(expected));
+    }
+}
+
+TEST(SysExCodec, Codec)
+{
+
+}
+
+END_UNNAMED_NAMESPACE
diff --git a/test/unit-tests/unit-tests.h b/test/unit-tests/unit-tests.h
index 520206b..b02f40c 100644
--- a/test/unit-tests/unit-tests.h
+++ b/test/unit-tests/unit-tests.h
@@ -2,6 +2,7 @@
 
 #include "unit-tests_Namespace.h"
 #include <gtest/gtest.h>
+#include <gmock/gmock.h>
 
 BEGIN_UNIT_TESTS_NAMESPACE