diff --git a/nsprpub/pr/include/md/_linux.cfg b/nsprpub/pr/include/md/_linux.cfg
index 301f4590068..70f1f9d7b8b 100644
--- a/nsprpub/pr/include/md/_linux.cfg
+++ b/nsprpub/pr/include/md/_linux.cfg
@@ -414,6 +414,97 @@
 #define PR_BYTES_PER_WORD_LOG2   2
 #define PR_BYTES_PER_DWORD_LOG2  3
 
+#elif defined(__s390__)
+
+#define IS_BIG_ENDIAN 1
+#undef  IS_LITTLE_ENDIAN
+
+#define PR_BYTES_PER_BYTE   1
+#define PR_BYTES_PER_SHORT  2
+#define PR_BYTES_PER_INT    4
+#define PR_BYTES_PER_INT64  8
+#define PR_BYTES_PER_LONG   4
+#define PR_BYTES_PER_FLOAT  4
+#define PR_BYTES_PER_DOUBLE 8
+#define PR_BYTES_PER_WORD   4
+#define PR_BYTES_PER_DWORD  8
+
+#define PR_BITS_PER_BYTE    8
+#define PR_BITS_PER_SHORT   16
+#define PR_BITS_PER_INT     32
+#define PR_BITS_PER_INT64   64
+#define PR_BITS_PER_LONG    32
+#define PR_BITS_PER_FLOAT   32
+#define PR_BITS_PER_DOUBLE  64
+#define PR_BITS_PER_WORD    32
+
+#define PR_BITS_PER_BYTE_LOG2   3
+#define PR_BITS_PER_SHORT_LOG2  4
+#define PR_BITS_PER_INT_LOG2    5
+#define PR_BITS_PER_INT64_LOG2  6
+#define PR_BITS_PER_LONG_LOG2   5
+#define PR_BITS_PER_FLOAT_LOG2  5
+#define PR_BITS_PER_DOUBLE_LOG2 6
+#define PR_BITS_PER_WORD_LOG2   5
+
+#define PR_ALIGN_OF_SHORT   2
+#define PR_ALIGN_OF_INT     4
+#define PR_ALIGN_OF_LONG    4
+#define PR_ALIGN_OF_INT64   4
+#define PR_ALIGN_OF_FLOAT   4
+#define PR_ALIGN_OF_DOUBLE  4
+#define PR_ALIGN_OF_POINTER 4
+#define PR_ALIGN_OF_WORD    4
+
+#define PR_BYTES_PER_WORD_LOG2   2
+#define PR_BYTES_PER_DWORD_LOG2  3
+
+#elif defined(__s390x__)
+
+#define IS_BIG_ENDIAN 1
+#undef  IS_LITTLE_ENDIAN
+#define IS_64
+
+#define PR_BYTES_PER_BYTE   1
+#define PR_BYTES_PER_SHORT  2
+#define PR_BYTES_PER_INT    4
+#define PR_BYTES_PER_INT64  8
+#define PR_BYTES_PER_LONG   8
+#define PR_BYTES_PER_FLOAT  4
+#define PR_BYTES_PER_DOUBLE 8
+#define PR_BYTES_PER_WORD   8
+#define PR_BYTES_PER_DWORD  8
+
+#define PR_BITS_PER_BYTE    8
+#define PR_BITS_PER_SHORT   16
+#define PR_BITS_PER_INT     32
+#define PR_BITS_PER_INT64   64
+#define PR_BITS_PER_LONG    64
+#define PR_BITS_PER_FLOAT   32
+#define PR_BITS_PER_DOUBLE  64
+#define PR_BITS_PER_WORD    64
+
+#define PR_BITS_PER_BYTE_LOG2   3
+#define PR_BITS_PER_SHORT_LOG2  4
+#define PR_BITS_PER_INT_LOG2    5
+#define PR_BITS_PER_INT64_LOG2  6
+#define PR_BITS_PER_LONG_LOG2   6
+#define PR_BITS_PER_FLOAT_LOG2  5
+#define PR_BITS_PER_DOUBLE_LOG2 6
+#define PR_BITS_PER_WORD_LOG2   6
+
+#define PR_ALIGN_OF_SHORT   2
+#define PR_ALIGN_OF_INT     4
+#define PR_ALIGN_OF_LONG    8
+#define PR_ALIGN_OF_INT64   8
+#define PR_ALIGN_OF_FLOAT   4
+#define PR_ALIGN_OF_DOUBLE  8
+#define PR_ALIGN_OF_POINTER 8
+#define PR_ALIGN_OF_WORD    8
+
+#define PR_BYTES_PER_WORD_LOG2   3
+#define PR_BYTES_PER_DWORD_LOG2  3
+
 #else
 
 #error "Unknown CPU architecture"
diff --git a/nsprpub/pr/include/md/_linux.h b/nsprpub/pr/include/md/_linux.h
index 04b2ea74458..df2cfd406b9 100644
--- a/nsprpub/pr/include/md/_linux.h
+++ b/nsprpub/pr/include/md/_linux.h
@@ -59,6 +59,10 @@
 #define _PR_SI_ARCHITECTURE "mips"
 #elif defined(__arm__)
 #define _PR_SI_ARCHITECTURE "arm"
+#elif defined(__s390__)
+#define _PR_SI_ARCHITECTURE "s390"
+#elif defined(__s390x__)
+#define _PR_SI_ARCHITECTURE "s390x"
 #else
 #error "Unknown CPU architecture"
 #endif
diff --git a/nsprpub/pr/src/io/prprf.c b/nsprpub/pr/src/io/prprf.c
index 95c165a41cb..4fa197c1569 100644
--- a/nsprpub/pr/src/io/prprf.c
+++ b/nsprpub/pr/src/io/prprf.c
@@ -51,8 +51,10 @@
 ** Note: on some platforms va_list is defined as an array,
 ** and requires array notation.
 */
-#if (defined(LINUX) && defined(__powerpc__)) || defined(WIN16) || \
-    defined(QNX) || \
+#if (defined(LINUX) && defined(__powerpc__)) || \
+    (defined(LINUX) && defined(__s390__)) || \
+    (defined(LINUX) && defined(__s390x__)) || \
+    defined(WIN16) || defined(QNX) || \
     (defined(__NetBSD__) && defined(__powerpc__) && \
     __NetBSD_Version__ < 105000000)
 #define VARARGS_ASSIGN(foo, bar) foo[0] = bar[0]