diff --git a/MultiSource/Applications/CMakeLists.txt b/MultiSource/Applications/CMakeLists.txt
--- a/MultiSource/Applications/CMakeLists.txt
+++ b/MultiSource/Applications/CMakeLists.txt
@@ -1,4 +1,7 @@
-add_subdirectory(JM)
+if(NOT TARGET_OS STREQUAL "OpenBSD")
+  add_subdirectory(JM)
+endif()
+
 add_subdirectory(SIBsim4)
 add_subdirectory(aha)
 add_subdirectory(d)
diff --git a/MultiSource/Applications/SPASS/clock.h b/MultiSource/Applications/SPASS/clock.h
--- a/MultiSource/Applications/SPASS/clock.h
+++ b/MultiSource/Applications/SPASS/clock.h
@@ -49,7 +49,9 @@
 
 #include "misc.h"
 #include <sys/types.h>
+#ifndef CLOCK_NO_TIMING
 #include <sys/timeb.h>
+#endif
 
 typedef enum {
   clock_BACKTRACK,
@@ -61,7 +63,9 @@
   clock_TYPESIZE
 } CLOCK_CLOCKS;
 
+#ifndef CLOCK_NO_TIMING
 typedef struct timeb CLOCK_TMS;
+#endif
 
 void   clock_Init(void);
 void   clock_InitCounter(CLOCK_CLOCKS);
diff --git a/MultiSource/Applications/SPASS/clock.c b/MultiSource/Applications/SPASS/clock.c
--- a/MultiSource/Applications/SPASS/clock.c
+++ b/MultiSource/Applications/SPASS/clock.c
@@ -53,7 +53,9 @@
 /**************************************************************/
 
 float      clock_Akku[clock_TYPESIZE];
+#ifndef CLOCK_NO_TIMING
 CLOCK_TMS  clock_Counters[clock_TYPESIZE];
+#endif
 
 #ifdef WIN
 float      clock_Ping;
diff --git a/MultiSource/Applications/minisat/Main.cpp b/MultiSource/Applications/minisat/Main.cpp
--- a/MultiSource/Applications/minisat/Main.cpp
+++ b/MultiSource/Applications/minisat/Main.cpp
@@ -65,7 +65,7 @@
 static inline uint64_t memUsed() { return (uint64_t)memReadStat(0) * (uint64_t)getpagesize(); }
 
 
-#elif defined(__FreeBSD__) || defined(__NetBSD__)
+#elif defined(__FreeBSD__) || defined(__NetBSD__) || defined(__OpenBSD__)
 static inline uint64_t memUsed(void) {
     struct rusage ru;
     getrusage(RUSAGE_SELF, &ru);
diff --git a/MultiSource/Benchmarks/MiBench/office-ispell/term.c b/MultiSource/Benchmarks/MiBench/office-ispell/term.c
--- a/MultiSource/Benchmarks/MiBench/office-ispell/term.c
+++ b/MultiSource/Benchmarks/MiBench/office-ispell/term.c
@@ -76,8 +76,9 @@
 #include "msgs.h"
 #include <signal.h>
 
-#if defined(__GLIBC__) || defined(__FreeBSD__) || defined(__NetBSD__) || defined(__APPLE__) || (defined(__sun__) && defined(__svr4__))
-/* Use termios under at least glibc */
+#if defined(__GLIBC__) || defined(__FreeBSD__) || defined(__NetBSD__) || \
+    defined(__OpenBSD__) || defined(__APPLE__) || \
+    (defined(__sun__) && defined(__svr4__))
 #include <termios.h>
 #define USE_TERMIOS
 #ifndef USG
diff --git a/SingleSource/Benchmarks/Misc/oourafft.c b/SingleSource/Benchmarks/Misc/oourafft.c
--- a/SingleSource/Benchmarks/Misc/oourafft.c
+++ b/SingleSource/Benchmarks/Misc/oourafft.c
@@ -2,7 +2,9 @@
 #include <memory.h>
 #include <stdio.h>
 #include <stdlib.h>
-#if !defined(__APPLE__) && !defined(__FreeBSD__) && !defined(__NetBSD__) && !defined(_AIX) // memalign
+/* memalign */
+#if !defined(__APPLE__) && !defined(__FreeBSD__) && !defined(__NetBSD__) && \
+    !defined(__OpenBSD__) && !defined(_AIX)
 #include <malloc.h>
 #endif
 
@@ -37,7 +39,9 @@
   t_overhead = t_end - t_start;
 
   /* Prepare aux data */
-#if !defined(__APPLE__) && !defined(__FreeBSD__) && !defined(__NetBSD__) && !defined(_AIX) /* Darwin always 16-byte aligns malloc data */
+  /* Darwin always 16-byte aligns malloc data */
+#if !defined(__APPLE__) && !defined(__FreeBSD__) && !defined(__NetBSD__) && \
+    !defined(__OpenBSD__) && !defined(_AIX)
   ip = memalign(16, sqrt(N)*sizeof(int));
   w  = memalign(16, 2*N*5/4*sizeof(double));
 #else
@@ -47,7 +51,9 @@
   makewt(N >> 1, ip, w);
   
   /* Allocate buffers */
-#if !defined(__APPLE__) && !defined(__FreeBSD__) && !defined(__NetBSD__) && !defined(_AIX) /* Darwin always 16-byte aligns malloc data */
+  /* Darwin always 16-byte aligns malloc data */
+#if !defined(__APPLE__) && !defined(__FreeBSD__) && !defined(__NetBSD__) && \
+    !defined(__OpenBSD__) && !defined(_AIX)
   ref = memalign(16, 2*N*sizeof(double));
   cmp = memalign(16, 2*N*sizeof(double));
   src = memalign(16, 2*N*sizeof(double));
@@ -188,8 +194,6 @@
 
 /* -------- initializing routines -------- */
 
-#include <math.h>
-
 void makewt(int nw, int *ip, double *w)
 {
   int j, nwh;
diff --git a/SingleSource/UnitTests/2005-05-11-Popcount-ffs-fls.c b/SingleSource/UnitTests/2005-05-11-Popcount-ffs-fls.c
--- a/SingleSource/UnitTests/2005-05-11-Popcount-ffs-fls.c
+++ b/SingleSource/UnitTests/2005-05-11-Popcount-ffs-fls.c
@@ -79,6 +79,11 @@
 #define ffsl ffs64
 #endif
 
+/* XXX */
+#if defined(__OpenBSD__)
+#define ffsl ffs
+#endif
+
 int i;
 int main(void) {
   long long l;