diff --git a/README.md b/README.md
index f158826..b389f65 100644
--- a/README.md
+++ b/README.md
@@ -41,6 +41,9 @@ Minmea runs out-of-the-box under most Unix-compatible systems. Support for non-U
 1. Define `MINMEA_INCLUDE_COMPAT` in the build environment.
 2. Add appropriate compatibility header from under `compat/` directory as `minmea_compat.h`.
 
+If your GPS receiver outputs very long sentences, consider increasing `MINMEA_MAX_SENTENCE_LENGTH`
+in your build environment.
+
 ## Fractional number format
 
 Internally, minmea stores fractional numbers as pairs of two integers: ``{value, scale}``.
diff --git a/minmea.h b/minmea.h
index c92f579..033a34d 100644
--- a/minmea.h
+++ b/minmea.h
@@ -23,7 +23,9 @@ extern "C" {
 #include <minmea_compat.h>
 #endif
 
+#ifndef MINMEA_MAX_SENTENCE_LENGTH
 #define MINMEA_MAX_SENTENCE_LENGTH 80
+#endif
 
 enum minmea_sentence_id {
     MINMEA_INVALID = -1,