diff --git a/src/nvim/tui/terminfo.c b/src/nvim/tui/terminfo.c
index 6c870d471d..493454d75c 100644
--- a/src/nvim/tui/terminfo.c
+++ b/src/nvim/tui/terminfo.c
@@ -347,7 +347,7 @@ String terminfo_info_msg(const TerminfoEntry *ti, const char *termname, bool fro
 
 static int push(long num, char *string, TPSTACK *stack)
 {
-  if (stack->offset >= sizeof(stack->nums)) {
+  if (stack->offset >= ARRAY_SIZE(stack->nums)) {
     return -1;
   }
   stack->nums[stack->offset] = num;
diff --git a/test/unit/tui/terminfo_spec.lua b/test/unit/tui/terminfo_spec.lua
new file mode 100644
index 0000000000..ae1d6d0833
--- /dev/null
+++ b/test/unit/tui/terminfo_spec.lua
@@ -0,0 +1,33 @@
+local t = require('test.unit.testutil')
+local itp = t.gen_itp(it)
+
+local ffi = t.ffi
+local cimport = t.cimport
+local to_cstr = t.to_cstr
+local eq = t.eq
+
+-- Import terminfo headers
+local terminfo = cimport('./src/nvim/tui/terminfo.h')
+
+describe('terminfo_fmt', function()
+  itp('stack overflow fails before producing output', function()
+    -- Creates a buffer
+    local buf = ffi.new('char[256]')
+    local buf_end = buf + ffi.sizeof(buf) -- One past end
+
+    -- Sets input parameters
+    local params = ffi.new('TPVAR[9]')
+    params[0].num = 65 -- 'A'
+    params[0].string = nil
+
+    -- 20 pushes (TPSTACK nums array limit) then prints one char
+    local valid_fmt = string.rep('%p1', 20) .. '%c'
+    local valid_n = terminfo.terminfo_fmt(buf, buf_end, to_cstr(valid_fmt), params)
+    eq(1, valid_n)
+
+    -- Overflows with 21 pushes and fails before print
+    local overflow_fmt = string.rep('%p1', 21) .. '%c'
+    local overflow_n = terminfo.terminfo_fmt(buf, buf_end, to_cstr(overflow_fmt), params)
+    eq(0, overflow_n)
+  end)
+end)