diff --git a/scripts/build.sh b/scripts/build.sh
index 1ec17ad..b7372e7 100755
--- a/scripts/build.sh
+++ b/scripts/build.sh
@@ -58,7 +58,7 @@ make an
 
 echo "==> Step 2/3: Build core (make ${TARGET} SSLTYPE=${SSLTYPE})"
 # IMPORTANT: do NOT use -j here; UW-IMAP's legacy build is not reliably parallel-safe.
-make "${TARGET}" "SSLTYPE=${SSLTYPE}"
+make "${TARGET}" "SSLTYPE=${SSLTYPE}" ""EXTRACFLAGS=-I/usr/include/openssl""
 
 echo "==> Step 3/3: Build bundled tools (make bundled)"
 # Bundled tools depend on generated headers like c-client/osdep.h.