diff --git a/runtime/pb/wire.lua b/runtime/pb/wire.lua
index 20dbd4241ae896e11520c3ff99850855311b8a4a..cb1cef8c976768d9950830d3b54fc2e2a3888b2e 100644
--- a/runtime/pb/wire.lua
+++ b/runtime/pb/wire.lua
@@ -276,6 +276,20 @@
 local function decode_float(buf, pos)
     if pos + 3 > #buf then error("truncated float", 0) end
     ffi.copy(F32.b, buf:sub(pos, pos + 3), 4)
+    -- Detect Inf/NaN from the raw bit pattern before going through
+    -- tonumber(). LuaJIT 2.1 NaN-boxes Lua values, so some IEEE NaN
+    -- payloads collide with internal type tags (nil/function/etc.) and
+    -- `tonumber(F32.f)` yields a non-number. Reading via F32.u (uint32)
+    -- keeps us in the integer domain until we decide what to return.
+    local u  = F32.u
+    local exp = bit.band(bit.rshift(u, 23), 0xff)
+    if exp == 0xff then
+        if bit.band(u, 0x7fffff) == 0 then
+            if bit.band(u, 0x80000000) ~= 0 then return -math.huge, pos + 4 end
+            return math.huge, pos + 4
+        end
+        return 0/0, pos + 4
+    end
     return tonumber(F32.f), pos + 4
 end
 M.decode_float = decode_float
@@ -286,9 +300,28 @@     return ffi.string(F64.b, 8)
 end
 M.encode_double = encode_double
 
+local F64_EXP_MASK  = UINT64(0x7ff)
+local F64_FRAC_MASK = UINT64(0xfffffffffffff)
+local F64_SIGN_BIT  = bit.lshift(UINT64(1), 63)
+
 local function decode_double(buf, pos)
     if pos + 7 > #buf then error("truncated double", 0) end
     ffi.copy(F64.b, buf:sub(pos, pos + 7), 8)
+    -- Detect Inf/NaN from the raw bit pattern before going through
+    -- tonumber(). LuaJIT 2.1 NaN-boxes Lua values, so some IEEE NaN
+    -- payloads collide with internal type tags (nil/function/etc.) and
+    -- `tonumber(F64.d)` yields a non-number. Reading via F64.u (uint64)
+    -- keeps us in the integer domain until we decide what to return.
+    local u = F64.u
+    if bit.band(bit.rshift(u, 52), F64_EXP_MASK) == F64_EXP_MASK then
+        if bit.band(u, F64_FRAC_MASK) == UINT64_ZERO then
+            if bit.band(u, F64_SIGN_BIT) ~= UINT64_ZERO then
+                return -math.huge, pos + 8
+            end
+            return math.huge, pos + 8
+        end
+        return 0/0, pos + 8
+    end
     return tonumber(F64.d), pos + 8
 end
 M.decode_double = decode_double