diff --git a/src/nm-initrd-generator/nmi-cmdline-reader.c b/src/nm-initrd-generator/nmi-cmdline-reader.c
index f6aa87b924..9606b45427 100644
--- a/src/nm-initrd-generator/nmi-cmdline-reader.c
+++ b/src/nm-initrd-generator/nmi-cmdline-reader.c
@@ -1205,6 +1205,11 @@ reader_parse_ethtool(Reader *reader, char *argument)
             _LOGW(LOGD_CORE, "Invalid value for rd.ethtool.speed, rd.ethtool.speed was not set");
     }
 
+    if (speed == 0 && autoneg == FALSE) {
+        _LOGW(LOGD_CORE,
+              "rd.ethtool: autoneg ignored. Cannot disable autoneg without setting speed");
+    }
+
     if (autoneg == -1)
         autoneg = FALSE;
 
diff --git a/src/nm-initrd-generator/tests/test-cmdline-reader.c b/src/nm-initrd-generator/tests/test-cmdline-reader.c
index 6f747fed1a..c20f8c29bd 100644
--- a/src/nm-initrd-generator/tests/test-cmdline-reader.c
+++ b/src/nm-initrd-generator/tests/test-cmdline-reader.c
@@ -2330,14 +2330,20 @@ test_rd_ethtool(void)
     _ethtool_check("rd.ethtool=eth0:on::", TRUE, 0);
     _ethtool_check("rd.ethtool=eth0:on:0:", TRUE, 0);
 
+    NMTST_EXPECT_NM_WARN("cmdline-reader: rd.ethtool: autoneg ignored. Cannot disable autoneg "
+                         "without setting speed");
     _ethtool_check("rd.ethtool=eth0:off", FALSE, 0);
 
     _ethtool_check("rd.ethtool=eth0:true", TRUE, 0);
 
+    NMTST_EXPECT_NM_WARN("cmdline-reader: rd.ethtool: autoneg ignored. Cannot disable autoneg "
+                         "without setting speed");
     _ethtool_check("rd.ethtool=eth0:false", FALSE, 0);
 
     _ethtool_check("rd.ethtool=eth0:1", TRUE, 0);
 
+    NMTST_EXPECT_NM_WARN("cmdline-reader: rd.ethtool: autoneg ignored. Cannot disable autoneg "
+                         "without setting speed");
     _ethtool_check("rd.ethtool=eth0:0", FALSE, 0);
 
     NMTST_EXPECT_NM_WARN(
@@ -2397,13 +2403,25 @@ test_rd_ethtool(void)
     NMTST_EXPECT_NM_WARN("cmdline-reader: Impossible to set rd.ethtool options: invalid format");
     _ethtool_check_inval("rd.ethtool=:::");
 
+    NMTST_EXPECT_NM_WARN("cmdline-reader: rd.ethtool: autoneg ignored. Cannot disable autoneg "
+                         "without setting speed");
     _ethtool_check_v(NM_MAKE_STRV("rd.ethtool=eth0:off:0", "rd.ethtool=eth0:on"), TRUE, 0);
+    NMTST_EXPECT_NM_WARN("cmdline-reader: rd.ethtool: autoneg ignored. Cannot disable autoneg "
+                         "without setting speed");
+    NMTST_EXPECT_NM_WARN("cmdline-reader: rd.ethtool: autoneg ignored. Cannot disable autoneg "
+                         "without setting speed");
     _ethtool_check_v(NM_MAKE_STRV("rd.ethtool=eth0:off:0", "rd.ethtool=eth0:off"), FALSE, 0);
     _ethtool_check_v(NM_MAKE_STRV("rd.ethtool=eth0:on:0", "rd.ethtool=eth0:on"), TRUE, 0);
+    NMTST_EXPECT_NM_WARN("cmdline-reader: rd.ethtool: autoneg ignored. Cannot disable autoneg "
+                         "without setting speed");
     _ethtool_check_v(NM_MAKE_STRV("rd.ethtool=eth0:on:0", "rd.ethtool=eth0:off"), FALSE, 0);
     _ethtool_check_v(NM_MAKE_STRV("rd.ethtool=eth0:off:100", "rd.ethtool=eth0:on"), TRUE, 0);
+    NMTST_EXPECT_NM_WARN("cmdline-reader: rd.ethtool: autoneg ignored. Cannot disable autoneg "
+                         "without setting speed");
     _ethtool_check_v(NM_MAKE_STRV("rd.ethtool=eth0:off:100", "rd.ethtool=eth0:off"), FALSE, 0);
     _ethtool_check_v(NM_MAKE_STRV("rd.ethtool=eth0:on:100", "rd.ethtool=eth0:on"), TRUE, 0);
+    NMTST_EXPECT_NM_WARN("cmdline-reader: rd.ethtool: autoneg ignored. Cannot disable autoneg "
+                         "without setting speed");
     _ethtool_check_v(NM_MAKE_STRV("rd.ethtool=eth0:on:100", "rd.ethtool=eth0:off"), FALSE, 0);
     _ethtool_check_v(NM_MAKE_STRV("rd.ethtool=eth0:off:100", "rd.ethtool=eth0:"), FALSE, 0);
 }