diff --git a/lib/std/debug.zig b/lib/std/debug.zig
index 44310de261..983d088374 100644
--- a/lib/std/debug.zig
+++ b/lib/std/debug.zig
@@ -110,27 +110,28 @@ pub fn getSelfDebugInfo() !*DebugInfo {
 }
 
 pub fn detectTTYConfig(file: std.fs.File) TTY.Config {
-    if (process.hasEnvVarConstant("ZIG_DEBUG_COLOR")) {
+    if (builtin.os.tag == .wasi) {
+        // Per https://github.com/WebAssembly/WASI/issues/162 ANSI codes
+        // aren't currently supported.
+        return .no_color;
+    } else if (process.hasEnvVarConstant("ZIG_DEBUG_COLOR")) {
         return .escape_codes;
     } else if (process.hasEnvVarConstant("NO_COLOR")) {
         return .no_color;
-    } else {
-        if (file.supportsAnsiEscapeCodes()) {
-            return .escape_codes;
-        } else if (native_os == .windows and file.isTty()) {
-            var info: windows.CONSOLE_SCREEN_BUFFER_INFO = undefined;
-            if (windows.kernel32.GetConsoleScreenBufferInfo(file.handle, &info) != windows.TRUE) {
-                // TODO: Should this return an error instead?
-                return .no_color;
-            }
-            return .{ .windows_api = .{
-                .handle = file.handle,
-                .reset_attributes = info.wAttributes,
-            } };
-        } else {
+    } else if (file.supportsAnsiEscapeCodes()) {
+        return .escape_codes;
+    } else if (native_os == .windows and file.isTty()) {
+        var info: windows.CONSOLE_SCREEN_BUFFER_INFO = undefined;
+        if (windows.kernel32.GetConsoleScreenBufferInfo(file.handle, &info) != windows.TRUE) {
+            // TODO: Should this return an error instead?
             return .no_color;
         }
+        return .{ .windows_api = .{
+            .handle = file.handle,
+            .reset_attributes = info.wAttributes,
+        } };
     }
+    return .no_color;
 }
 
 /// Tries to print the current stack trace to stderr, unbuffered, and ignores any error returned.
diff --git a/lib/std/process.zig b/lib/std/process.zig
index bcd0d5bfa9..138f5feeb8 100644
--- a/lib/std/process.zig
+++ b/lib/std/process.zig
@@ -369,6 +369,11 @@ pub fn getEnvVarOwned(allocator: Allocator, key: []const u8) GetEnvVarOwnedError
             error.UnexpectedSecondSurrogateHalf => return error.InvalidUtf8,
             else => |e| return e,
         };
+    } else if (builtin.os.tag == .wasi and !builtin.link_libc) {
+        var envmap = getEnvMap(allocator) catch return error.OutOfMemory;
+        defer envmap.deinit();
+        const val = envmap.get(key) orelse return error.EnvironmentVariableNotFound;
+        return allocator.dupe(u8, val);
     } else {
         const result = os.getenv(key) orelse return error.EnvironmentVariableNotFound;
         return allocator.dupe(u8, result);
@@ -379,6 +384,8 @@ pub fn hasEnvVarConstant(comptime key: []const u8) bool {
     if (builtin.os.tag == .windows) {
         const key_w = comptime std.unicode.utf8ToUtf16LeStringLiteral(key);
         return std.os.getenvW(key_w) != null;
+    } else if (builtin.os.tag == .wasi and !builtin.link_libc) {
+        @compileError("hasEnvVarConstant is not supported for WASI without libc");
     } else {
         return os.getenv(key) != null;
     }
@@ -390,6 +397,10 @@ pub fn hasEnvVar(allocator: Allocator, key: []const u8) error{OutOfMemory}!bool
         const key_w = try std.unicode.utf8ToUtf16LeWithNull(stack_alloc.get(), key);
         defer stack_alloc.allocator.free(key_w);
         return std.os.getenvW(key_w) != null;
+    } else if (builtin.os.tag == .wasi and !builtin.link_libc) {
+        var envmap = getEnvMap(allocator) catch return error.OutOfMemory;
+        defer envmap.deinit();
+        return envmap.getPtr(key) != null;
     } else {
         return os.getenv(key) != null;
     }
diff --git a/src/main.zig b/src/main.zig
index ba82efc294..007adb78ac 100644
--- a/src/main.zig
+++ b/src/main.zig
@@ -637,6 +637,10 @@ const Emit = union(enum) {
 };
 
 fn optionalStringEnvVar(arena: Allocator, name: []const u8) !?[]const u8 {
+    // Env vars aren't used in the bootstrap stage.
+    if (build_options.only_c) {
+        return null;
+    }
     if (std.process.getEnvVarOwned(arena, name)) |value| {
         return value;
     } else |err| switch (err) {
@@ -676,8 +680,8 @@ fn buildOutputType(
     var no_builtin = false;
     var watch = false;
     var debug_compile_errors = false;
-    var verbose_link = std.process.hasEnvVarConstant("ZIG_VERBOSE_LINK");
-    var verbose_cc = std.process.hasEnvVarConstant("ZIG_VERBOSE_CC");
+    var verbose_link = (builtin.os.tag != .wasi or builtin.link_libc) and std.process.hasEnvVarConstant("ZIG_VERBOSE_LINK");
+    var verbose_cc = (builtin.os.tag != .wasi or builtin.link_libc) and std.process.hasEnvVarConstant("ZIG_VERBOSE_CC");
     var verbose_air = false;
     var verbose_llvm_ir = false;
     var verbose_cimport = false;
@@ -859,7 +863,8 @@ fn buildOutputType(
     // before arg parsing, check for the NO_COLOR environment variable
     // if it exists, default the color setting to .off
     // explicit --color arguments will still override this setting.
-    color = if (std.process.hasEnvVarConstant("NO_COLOR")) .off else .auto;
+    // Disable color on WASI per https://github.com/WebAssembly/WASI/issues/162
+    color = if (builtin.os.tag == .wasi or std.process.hasEnvVarConstant("NO_COLOR")) .off else .auto;
 
     switch (arg_mode) {
         .build, .translate_c, .zig_test, .run => {