diff --git a/External/SPEC/SpecCPU2006.cmake b/External/SPEC/SpecCPU2006.cmake
--- a/External/SPEC/SpecCPU2006.cmake
+++ b/External/SPEC/SpecCPU2006.cmake
@@ -22,6 +22,16 @@
     list(APPEND CPPFLAGS -DSPEC_CPU_MACOSX)
   elseif(TARGET_OS STREQUAL "Linux")
     list(APPEND CPPFLAGS -DSPEC_CPU_LINUX)
+  elseif(TARGET_OS STREQUAL "FreeBSD")
+    list(APPEND CPPFLAGS -DSPEC_CPU_BSD)
+    # As support for SPEC_CPU_BSD is incomplete in SPEC2006, we also have to
+    # pass -DSPEC_CPU_MACOSX to avoid the use of gcvt() in 400.perlbench as
+    # this function is not available on FreeBSD. Additionally, this define
+    # ensures that all required functions are compiled in 483.xalancbmk and
+    # that complex.h is included in 462.libquantum.
+    list(APPEND CPPFLAGS -DSPEC_CPU_MACOSX)
+  else()
+    message(WARNING "Unsupported SPEC2006 TARGET_OS: ${TARGET_OS}")
   endif()
 
   if(ARCH STREQUAL "x86")