diff --git a/src/pixels.cpp b/src/pixels.cpp
index b0d7cb0..7dda8ce 100644
--- a/src/pixels.cpp
+++ b/src/pixels.cpp
@@ -9,9 +9,12 @@ static inline int t2p(int val) {
 }
 
 static void write(std::ostream& os, FILE* in) {
-    char* tc = getenv("TRUECOLOR");
-    std::string truecolor {tc ? tc : ""};
-    bool has_truecolor = truecolor.size() > 0;
+    char* tc = getenv("COLORTERM");
+    std::string colorterm {tc ? tc : ""};
+    bool has_truecolor = colorterm.size() > 0;
+    if (has_truecolor) {
+        has_truecolor = colorterm == "truecolor" || colorterm == "24bit";
+    }
     struct pam info;
     pnm_readpaminit(in, &info, PAM_STRUCT_SIZE(tuple_type));
     std::unique_ptr<tuple, void(*)(void*)> row1 {pnm_allocpamrow(&info), pm_freerow};