diff --git a/Makefile b/Makefile
index 6ba7800..3205aed 100644
--- a/Makefile
+++ b/Makefile
@@ -20,6 +20,9 @@ TARGET = pcapmirror
 
 # Installation directory
 PREFIX = /usr
+ifdef prefix
+PREFIX = $(prefix)
+endif
 
 # Default rule
 all: $(TARGET) man