diff --git a/configure.ac b/configure.ac
index 4f4bfcc1..0dea296c 100644
--- a/configure.ac
+++ b/configure.ac
@@ -48,7 +48,7 @@ AC_TYPE_UINT8_T
 AC_CHECK_TYPES([ptrdiff_t])
 
 # Checks for library functions.
-AC_CHECK_FUNCS([malloc realloc getcwd gettimeofday memmove memset regcomp setlocale sqrt strdup strndup])
+AC_CHECK_FUNCS([malloc realloc drand48 getcwd gettimeofday memmove memset regcomp setlocale sqrt strdup strndup])
 
 AC_CONFIG_FILES([Makefile
                  libpostal.pc
diff --git a/src/klib/drand48.c b/src/klib/drand48.c
index ab9230e3..2f4335bd 100644
--- a/src/klib/drand48.c
+++ b/src/klib/drand48.c
@@ -12,7 +12,11 @@
  * to anyone/anything when using this software.
 */
 
-//I've rearranged the source into a header-only implementation for drand48()   -Benjamin Kusin
+#ifdef HAVE_CONFIG_H
+#include <config.h>
+#endif
+
+#ifndef HAVE_DRAND48
 
 #include <math.h>
 #include "drand48.h"
@@ -67,4 +71,6 @@ double erand48(unsigned short xseed[3])
 double drand48(void)
 {
 	return erand48(_rand48_seed);
-}
\ No newline at end of file
+}
+
+#endif // HAVE_DRAND48
diff --git a/src/klib/drand48.h b/src/klib/drand48.h
index d8fd0f7d..56b55d3c 100644
--- a/src/klib/drand48.h
+++ b/src/klib/drand48.h
@@ -12,11 +12,15 @@
  * to anyone/anything when using this software.
 */
 
-//I've rearranged the source into a header-only implementation for drand48()   -Benjamin Kusin
-
 #ifndef _DRAND48_H
 #define _DRAND48_H
 
+#ifdef HAVE_CONFIG_H
+#include <config.h>
+#endif
+
+#ifndef HAVE_DRAND48
+
 #define	RAND48_SEED_0	(0x330e)
 #define	RAND48_SEED_1	(0xabcd)
 #define	RAND48_SEED_2	(0x1234)
@@ -37,5 +41,7 @@ double erand48(unsigned short xseed[3]);
 
 double drand48(void);
 
+#endif // HAVE_DRAND48
+
+#endif  // _DRAND48_H
 
-#endif  // _DRAND48_H
\ No newline at end of file
diff --git a/src/strndup.c b/src/strndup.c
index 61f605b6..6d1a9300 100644
--- a/src/strndup.c
+++ b/src/strndup.c
@@ -1,4 +1,7 @@
+#ifdef HAVE_CONFIG_H
 #include <config.h>
+#endif
+
 #ifndef HAVE_STRNDUP
 
 #include <stdlib.h>
diff --git a/src/strndup.h b/src/strndup.h
index 69dea1a7..7cd3bffb 100644
--- a/src/strndup.h
+++ b/src/strndup.h
@@ -1,7 +1,9 @@
 #ifndef STRNDUP_H
 #define STRNDUP_H
 
+#ifdef HAVE_CONFIG_H
 #include <config.h>
+#endif
 
 #ifndef HAVE_STRNDUP
 
diff --git a/windows/configure.ac b/windows/configure.ac
index b41080f6..0a964cf5 100644
--- a/windows/configure.ac
+++ b/windows/configure.ac
@@ -48,7 +48,7 @@ AC_TYPE_UINT8_T
 AC_CHECK_TYPES([ptrdiff_t])
 
 # Checks for library functions.
-AC_CHECK_FUNCS([malloc realloc getcwd gettimeofday memmove memset regcomp setlocale sqrt strdup strndup])
+AC_CHECK_FUNCS([malloc realloc drand48 getcwd gettimeofday memmove memset regcomp setlocale sqrt strdup strndup])
 
 AC_CONFIG_FILES([Makefile
                  libpostal.pc