diff --git a/src/common.cpp b/src/common.cpp
index 2a858c01f..b03aad111 100644
--- a/src/common.cpp
+++ b/src/common.cpp
@@ -1415,10 +1415,13 @@ static void validate_new_termsize(struct winsize *new_termsize) {
 /// Export the new terminal size as env vars and to the kernel if possible.
 static void export_new_termsize(struct winsize *new_termsize) {
     wchar_t buf[64];
+    env_var_t cols = env_get_string(L"COLUMNS", ENV_EXPORT);
     swprintf(buf, 64, L"%d", (int)new_termsize->ws_col);
-    env_set(L"COLUMNS", buf, ENV_EXPORT | ENV_GLOBAL);
+    env_set(L"COLUMNS", buf, ENV_GLOBAL | (cols.missing_or_empty() ? 0 : ENV_EXPORT));
+
+    env_var_t lines = env_get_string(L"LINES", ENV_EXPORT);
     swprintf(buf, 64, L"%d", (int)new_termsize->ws_row);
-    env_set(L"LINES", buf, ENV_EXPORT | ENV_GLOBAL);
+    env_set(L"LINES", buf, ENV_GLOBAL | (lines.missing_or_empty() ? 0 : ENV_EXPORT));
 
 #ifdef HAVE_WINSIZE
     ioctl(STDOUT_FILENO, TIOCSWINSZ, new_termsize);
diff --git a/src/env.cpp b/src/env.cpp
index c4a2cd517..106bed009 100644
--- a/src/env.cpp
+++ b/src/env.cpp
@@ -474,9 +474,10 @@ static void setup_path() {
 /// adjusted.
 static void env_set_termsize() {
     env_var_t cols = env_get_string(L"COLUMNS");
-    if (cols.missing_or_empty()) env_set(L"COLUMNS", DFLT_TERM_COL_STR, ENV_EXPORT | ENV_GLOBAL);
+    if (cols.missing_or_empty()) env_set(L"COLUMNS", DFLT_TERM_COL_STR, ENV_GLOBAL);
+
     env_var_t rows = env_get_string(L"LINES");
-    if (rows.missing_or_empty()) env_set(L"LINES", DFLT_TERM_ROW_STR, ENV_EXPORT | ENV_GLOBAL);
+    if (rows.missing_or_empty()) env_set(L"LINES", DFLT_TERM_ROW_STR, ENV_GLOBAL);
 }
 
 bool env_set_pwd() {